Allow nested #includes in extconfig.conf

extconfig.conf was hard-coded to not allow nested includes for some reason.
The code has been this way since a patch was merged for ASTERISK-3333 (revision
4889), which was a significant update to this code ("Merge config updates").

I can't figure out any good reason why this should be limited.  This patch just
removes the limit and uses the default nesting depth limit.

Closes issue ASTERISK-17837

Review: https://reviewboard.asterisk.org/r/3159/
........

Merged revisions 406643 from http://svn.asterisk.org/svn/asterisk/branches/1.8


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@406644 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/config.c

@@ -2287,7 +2287,6 @@ int read_config_maps(void)
 		ast_log(LOG_ERROR, "Unable to allocate memory for new config\n");
 		return -1;
 	}
-	configtmp->max_include_level = 1;
 	config = ast_config_internal_load(extconfig_conf, configtmp, flags, "", "extconfig");
 	if (config == CONFIG_STATUS_FILEINVALID) {
 		return -1;