patch 8.0.1711: term_setsize() is not implemented yet

Problem:    Term_setsize() is not implemented yet.
Solution:   Implement it.
diff --git a/src/terminal.c b/src/terminal.c
index f980a09..09d4887 100644
--- a/src/terminal.c
+++ b/src/terminal.c
@@ -40,7 +40,6 @@
  * TODO:
  * - Win32: Make terminal used for :!cmd in the GUI work better.  Allow for
  *   redirection.  Probably in call to channel_set_pipes().
- * - implement term_setsize()
  * - add an optional limit for the scrollback size.  When reaching it remove
  *   10% at the start.
  * - Copy text in the vterm to the Vim buffer once in a while, so that
@@ -4603,6 +4602,31 @@
 }
 
 /*
+ * "term_setsize(buf, rows, cols)" function
+ */
+    void
+f_term_setsize(typval_T *argvars UNUSED, typval_T *rettv UNUSED)
+{
+    buf_T	*buf = term_get_buf(argvars, "term_setsize()");
+    term_T	*term;
+    varnumber_T rows, cols;
+
+    if (buf == NULL || buf->b_term->tl_vterm == NULL)
+	return;
+    term = buf->b_term;
+    rows = get_tv_number(&argvars[1]);
+    rows = rows <= 0 ? term->tl_rows : rows;
+    cols = get_tv_number(&argvars[2]);
+    cols = cols <= 0 ? term->tl_cols : cols;
+    vterm_set_size(term->tl_vterm, rows, cols);
+    /* handle_resize() will resize the windows */
+
+    /* Get and remember the size we ended up with.  Update the pty. */
+    vterm_get_size(term->tl_vterm, &term->tl_rows, &term->tl_cols);
+    term_report_winsize(term, term->tl_rows, term->tl_cols);
+}
+
+/*
  * "term_getstatus(buf)" function
  */
     void
@@ -5432,7 +5456,7 @@
 }
 
 /*
- * Request size to terminal.
+ * Report the size to the terminal.
  */
     static void
 term_report_winsize(term_T *term, int rows, int cols)
@@ -5514,7 +5538,7 @@
 }
 
 /*
- * Request size to terminal.
+ * Report the size to the terminal.
  */
     static void
 term_report_winsize(term_T *term, int rows, int cols)