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/gui.c b/src/gui.c
index 8677787..9278df9 100644
--- a/src/gui.c
+++ b/src/gui.c
@@ -2750,7 +2750,7 @@
 		    vim_snprintf((char *)IObuff, IOSIZE,
 			    "INTERNAL ERROR: NUL in ScreenLines in row %ld",
 			    (long)gui.row);
-		    msg(IObuff);
+		    msg((char *)IObuff);
 		}
 	    }
 # ifdef FEAT_GUI_GTK
@@ -5323,7 +5323,7 @@
 		}
 	    }
 	    else
-		MSG(_("No match at cursor, finding next"));
+		msg(_("No match at cursor, finding next"));
 	    vim_regfree(regmatch.regprog);
 	}
     }