add warning if you try to use the _. exten (bug #4032)

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/v1-0@5472 65c4cc65-6c06-0410-ace0-fbb531ad65f3

pbx/pbx_config.c

@@ -1700,6 +1700,8 @@ static int pbx_load_module(void)
 							while(*appl && (*appl < 33)) appl++;
 							pbx_substitute_variables_helper(NULL, ext, realext, sizeof(realext) - 1);
 							if (ipri) {
+								if (!strcmp(realext, "_."))
+									ast_log(LOG_WARNING, "The use of '_.' for an extension is strongly discouraged and can have unexpected behavior.  Please use '_X.' instead at line %d\n", v->lineno);
 								if (ast_add_extension2(con, 0, realext, ipri, cidmatch, appl, strdup(data), FREE, registrar)) {
 									ast_log(LOG_WARNING, "Unable to register extension at line %d\n", v->lineno);
 								}