patch 8.2.1608: Vim9: getchar() test fails with GUI

Problem:    Vim9: getchar() test fails with GUI.
Solution:   Avoid that getchar(0) gets stuck on K_IGNORE.

Author: brammool

src/getchar.c

@@ -2044,10 +2044,12 @@ f_getchar(typval_T *argvars, typval_T *rettv)
 	    // illegal argument or getchar(0) and no char avail: return zero
 	    n = 0;
 	else
-	    // getchar(0) and char avail: return char
-	    n = plain_vgetc();
+	    // getchar(0) and char avail() != NUL: get a character.
+	    // Note that vpeekc_any() returns K_SPECIAL for K_IGNORE.
+	    n = safe_vgetc();
 
-	if (n == K_IGNORE || n == K_MOUSEMOVE)
+	if (n == K_IGNORE || n == K_MOUSEMOVE
+		|| n == K_VER_SCROLLBAR || n == K_HOR_SCROLLBAR)
 	    continue;
 	break;
     }

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1608,
 /**/
     1607,
 /**/