patch 8.2.4002: first char typed in Select mode can be wrong

Problem:    First char typed in Select mode can be wrong.
Solution:   Escape special bytes in the input buffer. (closes #9469)
diff --git a/src/getchar.c b/src/getchar.c
index fa8c574..6fecc1a 100644
--- a/src/getchar.c
+++ b/src/getchar.c
@@ -1121,7 +1121,7 @@
     int
 ins_char_typebuf(int c, int modifier)
 {
-    char_u	buf[MB_MAXBYTES + 4];
+    char_u	buf[MB_MAXBYTES * 3 + 4];
     int		len = 0;
 
     if (modifier != 0)
@@ -1142,8 +1142,18 @@
     }
     else
     {
-	len += (*mb_char2bytes)(c, buf + len);
-	buf[len] = NUL;
+	char_u	*p = buf + len;
+	int	char_len = (*mb_char2bytes)(c, p);
+#ifdef FEAT_GUI
+	int	save_gui_in_use = gui.in_use;
+
+	gui.in_use = FALSE;
+#endif
+	// if the character contains CSI or K_SPECIAL bytes they need escaping
+	len += fix_input_buffer(p, char_len);
+#ifdef FEAT_GUI
+	gui.in_use = save_gui_in_use;
+#endif
     }
     (void)ins_typebuf(buf, KeyNoremap, 0, !KeyTyped, cmd_silent);
     return len;
@@ -3644,7 +3654,6 @@
 	    p += 2;
 	    i -= 2;
 	}
-# ifndef MSWIN
 	// When the GUI is not used CSI needs to be escaped.
 	else if (!gui.in_use && p[0] == CSI)
 	{
@@ -3654,7 +3663,6 @@
 	    *p = (int)KE_CSI;
 	    len += 2;
 	}
-# endif
 	else
 #endif
 	if (p[0] == NUL || (p[0] == K_SPECIAL