Revert alloc_str changes

This reverts commit fdead26ffe.
This reverts commit 3e2419ebe3.
This reverts commit 17ce69b47a.

src/libstrongswan/settings.h

@@ -146,31 +146,13 @@ struct settings_t {
 	/**
 	 * Get a settings value as a string.
 	 *
-	 * This functions returns a string held by settings_t. It is not thread
-	 * save, a thread calling load_files might free the returned string at
-	 * any time. Use the thread save alloc_str if a different thread might
-	 * call load_files() or set_str().
-	 *
 	 * @param key		key including sections, printf style format
 	 * @param def		value returned if key not found
 	 * @param ...		argument list for key
-	 * @return			value pointing to internal string, not to be freed
+	 * @return			value pointing to internal string
 	 */
 	char* (*get_str)(settings_t *this, char *key, char *def, ...);
 
-	/**
-	 * Get a settings value as a string, thread save variant.
-	 *
-	 * This function is identical to get_str, but is thread save. It allocates
-	 * a copy for the returned string which must be freed.
-	 *
-	 * @param key		key including sections, printf style format
-	 * @param def		value returned if key not found
-	 * @param ...		argument list for key
-	 * @return			allocated string, to be free
-	 */
-	char* (*alloc_str)(settings_t *this, char *key, char *def, ...);
-
 	/**
 	 * Get a boolean yes|no, true|false value.
 	 *