patch 9.0.0100: get hit-enter prompt for system() when '!' is in 'guioptions'

Problem:    Get hit-enter prompt for system() when '!' is in 'guioptions'.
Solution:   Do not call wait_return() when not redrawing. (closes #3327)
diff --git a/src/version.c b/src/version.c
index c0a0315..9e682a5 100644
--- a/src/version.c
+++ b/src/version.c
@@ -736,6 +736,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    100,
+/**/
     99,
 /**/
     98,