patch 8.1.0779: argument for message functions is inconsistent

Problem:    Argument for message functions is inconsistent.
Solution:   Make first argument to msg() "char *".
diff --git a/src/regexp.c b/src/regexp.c
index 06076fd..accd10c 100644
--- a/src/regexp.c
+++ b/src/regexp.c
@@ -8199,8 +8199,8 @@
     if (p_verbose > 0)
     {
 	verbose_enter();
-	MSG_PUTS(_("Switching to backtracking RE engine for pattern: "));
-	MSG_PUTS(pat);
+	msg_puts(_("Switching to backtracking RE engine for pattern: "));
+	msg_puts((char *)pat);
 	verbose_leave();
     }
 }