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)

src/version.c

@@ -771,6 +771,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1099,
 /**/
     1098,
 /**/