Revert "remove default definition of SITE_TITLE; rename to _SITE_TITLE as with other constants of this nature"

This reverts commit 1f56ba13cd.

config.php-dist

@@ -186,6 +186,9 @@
 	// Users may enable other user plugins from Preferences/Plugins but may not
 	// disable plugins specified in this list.
 
+    define('SITE_TITLE', 'Tiny Tiny RSS');
+    // Change this value to customize the HTML page title
+
 	define('CONFIG_VERSION', 26);
 	// Expected config version. Please update this option in config.php
 	// if necessary (after migrating all new options from this file).

include/functions.php

@@ -4086,10 +4086,10 @@
 	}
 
     function get_site_title() {
-        if (defined("_SITE_TITLE")) {
-            return _SITE_TITLE;
-        } else {
-	        return "Tiny Tiny RSS";
-		  }
+        $original_title = "Tiny Tiny RSS";
+        if (defined("SITE_TITLE")) {
+            return SITE_TITLE;
+        }
+        return $original_title;
     }
 ?>