Docs: Add missing DocBlock for the _() function in compat.php.

Follow-up to [3901], [17603], [17620].

Props justlevine.
See #63268.
Built from https://develop.svn.wordpress.org/trunk@60312


git-svn-id: http://core.svn.wordpress.org/trunk@59648 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/compat.php

@@ -13,6 +13,16 @@
 
 // If gettext isn't available.
 if ( ! function_exists( '_' ) ) {
+	/**
+	 * Compat function to mimic _(), an alias of gettext().
+	 *
+	 * @since 0.71
+	 *
+	 * @see https://php.net/manual/en/function.gettext.php
+	 *
+	 * @param string $message The message being translated.
+	 * @return string
+	 */
 	function _( $message ) {
 		return $message;
 	}

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.9-alpha-60311';
+$wp_version = '6.9-alpha-60312';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.