patch 8.2.3879: getreg() and getregtype() contain dead code

Problem:    getreg() and getregtype() contain dead code.
Solution:   Remove the needless check. (closes #9392)  Also refactor to put
            common code in a shared function.

src/version.c

@@ -749,6 +749,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3879,
 /**/
     3878,
 /**/