patch 8.1.2389: using old C style comments

Problem:    Using old C style comments.
Solution:   Use // comments where appropriate.
diff --git a/src/libvterm/include/vterm.h b/src/libvterm/include/vterm.h
index 28d0a10..0238226 100644
--- a/src/libvterm/include/vterm.h
+++ b/src/libvterm/include/vterm.h
@@ -216,14 +216,13 @@
 // Parser layer
 // ------------
 
-/* Flag to indicate non-final subparameters in a single CSI parameter.
- * Consider
- *   CSI 1;2:3:4;5a
- * 1 4 and 5 are final.
- * 2 and 3 are non-final and will have this bit set
- *
- * Don't confuse this with the final byte of the CSI escape; 'a' in this case.
- */
+// Flag to indicate non-final subparameters in a single CSI parameter.
+// Consider
+//   CSI 1;2:3:4;5a
+// 1 4 and 5 are final.
+// 2 and 3 are non-final and will have this bit set
+//
+// Don't confuse this with the final byte of the CSI escape; 'a' in this case.
 #define CSI_ARG_FLAG_MORE (1U<<31)
 #define CSI_ARG_MASK      (~(1U<<31))
 
@@ -357,7 +356,7 @@
 void  vterm_screen_set_callbacks(VTermScreen *screen, const VTermScreenCallbacks *callbacks, void *user);
 void *vterm_screen_get_cbdata(VTermScreen *screen);
 
-/* Only invokes control, csi, osc, dcs */
+// Only invokes control, csi, osc, dcs
 void  vterm_screen_set_unrecognised_fallbacks(VTermScreen *screen, const VTermParserCallbacks *fallbacks, void *user);
 void *vterm_screen_get_unrecognised_fbdata(VTermScreen *screen);
 
diff --git a/src/libvterm/src/screen.c b/src/libvterm/src/screen.c
index 6ad0e1a..bf2383a 100644
--- a/src/libvterm/src/screen.c
+++ b/src/libvterm/src/screen.c
@@ -773,7 +773,7 @@
   cell->bg = intcell->pen.bg;
 
   if(vterm_get_special_pty_type() == 2) {
-    /* Get correct cell width from cell information contained in line buffer */
+    // Get correct cell width from cell information contained in line buffer
     if(pos.col < (screen->cols - 1) &&
        getcell(screen, pos.row, pos.col + 1)->chars[0] == (uint32_t)-1) {
       if(getcell(screen, pos.row, pos.col)->chars[0] == 0x20) {
@@ -798,8 +798,10 @@
   return 1;
 }
 
-// Copy external to internal representation of a screen cell
-/* static because it's only used internally for sb_popline during resize */
+/*
+ * Copy external to internal representation of a screen cell
+ * static because it's only used internally for sb_popline during resize
+ */
 static int vterm_screen_set_cell(VTermScreen *screen, VTermPos pos, const VTermScreenCell *cell)
 {
   ScreenCell *intcell = getcell(screen, pos.row, pos.col);
diff --git a/src/libvterm/src/unicode.c b/src/libvterm/src/unicode.c
index 7f93763..424b3e2 100644
--- a/src/libvterm/src/unicode.c
+++ b/src/libvterm/src/unicode.c
@@ -452,7 +452,7 @@
 }
 #endif
 
-#if 0 /* unused */
+#if 0 // unused
 static int mk_wcswidth(const uint32_t *pwcs, size_t n)
 {
   int w, width = 0;
@@ -479,8 +479,8 @@
 static int mk_wcwidth_cjk(uint32_t ucs)
 {
 #endif
-  /* sorted list of non-overlapping intervals of East Asian Ambiguous
-   * characters, generated by "uniset +WIDTH-A -cat=Me -cat=Mn -cat=Cf c" */
+  // sorted list of non-overlapping intervals of East Asian Ambiguous
+  // characters, generated by "uniset +WIDTH-A -cat=Me -cat=Mn -cat=Cf c"
   static const struct interval ambiguous[] = {
     { 0x00A1, 0x00A1 }, { 0x00A4, 0x00A4 }, { 0x00A7, 0x00A8 },
     { 0x00AA, 0x00AA }, { 0x00AE, 0x00AE }, { 0x00B0, 0x00B4 },
diff --git a/src/libvterm/src/vterm.c b/src/libvterm/src/vterm.c
index d17f06c..1d6a977 100644
--- a/src/libvterm/src/vterm.c
+++ b/src/libvterm/src/vterm.c
@@ -10,9 +10,9 @@
 
 #include "utf8.h"
 
-/*****************
- * API functions *
- *****************/
+///////////////////
+// API functions //
+///////////////////
 
 static void *default_malloc(size_t size, void *allocdata UNUSED)
 {
diff --git a/src/libvterm/t/harness.c b/src/libvterm/t/harness.c
index e2c7295..ccb2b39 100644
--- a/src/libvterm/t/harness.c
+++ b/src/libvterm/t/harness.c
@@ -1,5 +1,5 @@
 #include "vterm.h"
-#include "../src/vterm_internal.h" /* We pull in some internal bits too */
+#include "../src/vterm_internal.h" // We pull in some internal bits too
 
 #include <stdio.h>
 #include <string.h>
@@ -163,16 +163,16 @@
 }
 
 static VTermParserCallbacks parser_cbs = {
-  parser_text, /* text */
-  parser_control, /* control */
-  parser_escape, /* escape */
-  parser_csi, /* csi */
-  parser_osc, /* osc */
-  parser_dcs, /* dcs */
-  NULL /* resize */
+  parser_text, // text
+  parser_control, // control
+  parser_escape, // escape
+  parser_csi, // csi
+  parser_osc, // osc
+  parser_dcs, // dcs
+  NULL // resize
 };
 
-/* These callbacks are shared by State and Screen */
+// These callbacks are shared by State and Screen
 
 static int want_movecursor = 0;
 static VTermPos state_pos;
@@ -241,7 +241,7 @@
   return 0;
 }
 
-/* These callbacks are for State */
+// These callbacks are for State
 
 static int want_state_putglyph = 0;
 static int state_putglyph(VTermGlyphInfo *info, VTermPos pos, void *user)
@@ -333,17 +333,17 @@
 }
 
 VTermStateCallbacks state_cbs = {
-  state_putglyph, /* putglyph */
-  movecursor, /* movecursor */
-  scrollrect, /* scrollrect */
-  moverect, /* moverect */
-  state_erase, /* erase */
-  NULL, /* initpen */
-  state_setpenattr, /* setpenattr */
-  settermprop, /* settermprop */
-  NULL, /* bell */
-  NULL, /* resize */
-  state_setlineinfo, /* setlineinfo */
+  state_putglyph, // putglyph
+  movecursor, // movecursor
+  scrollrect, // scrollrect
+  moverect, // moverect
+  state_erase, // erase
+  NULL, // initpen
+  state_setpenattr, // setpenattr
+  settermprop, // settermprop
+  NULL, // bell
+  NULL, // resize
+  state_setlineinfo, // setlineinfo
 };
 
 static int want_screen_damage = 0;
@@ -427,7 +427,7 @@
   if(!want_screen_scrollback)
     return 0;
 
-  /* All lines of scrollback contain "ABCDE" */
+  // All lines of scrollback contain "ABCDE"
   for(col = 0; col < cols; col++) {
     if(col < 5)
       cells[col].chars[0] = 'A' + col;
@@ -442,14 +442,14 @@
 }
 
 VTermScreenCallbacks screen_cbs = {
-  screen_damage, /* damage */
-  moverect, /* moverect */
-  movecursor, /* movecursor */
-  settermprop, /* settermprop */
-  NULL, /* bell */
-  NULL, /* resize */
-  screen_sb_pushline, /* sb_pushline */
-  screen_sb_popline /* sb_popline */
+  screen_damage, // damage
+  moverect, // moverect
+  movecursor, // movecursor
+  settermprop, // settermprop
+  NULL, // bell
+  NULL, // resize
+  screen_sb_pushline, // sb_pushline
+  screen_sb_popline // sb_popline
 };
 
 int main(int argc, char **argv)
@@ -592,9 +592,8 @@
     }
 
     else if(streq(line, "WANTENCODING")) {
-      /* This isn't really external API but it's hard to get this out any
-       * other way
-       */
+      // This isn't really external API but it's hard to get this out any
+      // other way
       encoding.enc = vterm_lookup_encoding(ENC_UTF8, 'u');
       if(encoding.enc->init)
         (*encoding.enc->init)(encoding.enc, encoding.data);
@@ -833,7 +832,7 @@
         else if(len == 0)
           printf("\n");
         else {
-          /* Put an overwrite guard at both ends of the buffer */
+          // Put an overwrite guard at both ends of the buffer
           unsigned char *buffer = malloc(len + 4);
           unsigned char *text = buffer + 2;
           text[-2] = 0x55; text[-1] = 0xAA;