Introduce is_textdomain_loaded(). Fixes #10527 props nbachiyski.

git-svn-id: https://develop.svn.wordpress.org/trunk@13304 602fd350-edb4-49c9-b593-d223f7449a82

wp-includes/l10n.php

@@ -438,6 +438,18 @@ function &get_translations_for_domain( $domain ) {
 	return $l10n[$domain];
 }
 
+/**
+ * Whether there are translations for the domain
+ *
+ * @since 3.0.0
+ * @param string $domain
+ * @return bool Whether there are translations
+ */
+function is_textdomain_loaded( $domain ) {
+	global $l10n;
+	return isset( $l10n[$domain] );
+}
+
 /**
  * Translates role name. Since the role names are in the database and
  * not in the source there are dummy gettext calls to get them into the POT