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/if_mzsch.c b/src/if_mzsch.c
index 503a1e4..16c4c88 100644
--- a/src/if_mzsch.c
+++ b/src/if_mzsch.c
@@ -1574,7 +1574,7 @@
 	if (error)
 	    emsg(prev);
 	else
-	    MSG(prev);
+	    msg(prev);
 	prev = p + 1;
 	p = strchr(prev, '\n');
     }
@@ -1582,7 +1582,7 @@
     if (error)
 	emsg(prev);
     else
-	MSG(prev);
+	msg(prev);
 }
 
     static void