patch 8.1.0632: using sign group names is inefficient

Problem:    Using sign group names is inefficient.
Solution:   Store group names in a hash table and use a reference to them.
            Also remove unnecessary use of ":exe" from the tests.  (Yegappan
            Lakshmanan, closes #3715)
diff --git a/src/version.c b/src/version.c
index d53ffac..2452ae0 100644
--- a/src/version.c
+++ b/src/version.c
@@ -800,6 +800,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    632,
+/**/
     631,
 /**/
     630,