patch 8.1.1099: the do_tag() function is too long

Problem:    The do_tag() function is too long.
Solution:   Factor parts out to separate functions.  Move simplify_filename()
            to a file where it fits better. (Andy Massimino, closes #4195)
diff --git a/src/version.c b/src/version.c
index c82a153..1b38d29 100644
--- a/src/version.c
+++ b/src/version.c
@@ -772,6 +772,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1099,
+/**/
     1098,
 /**/
     1097,