patch 8.1.0280: 'incsearch' highlighting does not work for ":g!/"

Problem:    'incsearch' highlighting does not work for ":g!/".
Solution:   Skip the exclamation mark. (Hirohito Higashi)
diff --git a/src/ex_getln.c b/src/ex_getln.c
index 8765ac5..fb16743 100644
--- a/src/ex_getln.c
+++ b/src/ex_getln.c
@@ -298,6 +298,13 @@
 			    || STRNCMP(cmd, "global", p - cmd) == 0
 			    || STRNCMP(cmd, "vglobal", p - cmd) == 0))
 		{
+		    // Check for "global!/".
+		    if (*cmd == 'g' && *p == '!')
+		    {
+			p++;
+			if (*skipwhite(p) == NUL)
+			    return FALSE;
+		    }
 		    p = skipwhite(p);
 		    delim = *p++;
 		    end = skip_regexp(p, delim, p_magic, NULL);