BUG: db versions greater than 10 are failing a version check

Bug 1465107: Use Bootstrap CSS Framework
EG:  '10.0.19'  <  '5.0.25'  evaluates as false

Change string check to check float value instead.

Change-Id: I27809e38a176e0f6b5182f878904c28a772cda6e

htdocs/init.php

@@ -215,7 +215,7 @@ try {
         $okversion = '5.0.25';
         $dbfriendlyname = 'MySQL';
     }
-    if ($dbversion['version'] < $okversion) {
+    if (floatval($dbversion['version']) <  floatval($okversion)) {
         throw new ConfigSanityException(get_string('dbversioncheckfailed', 'error', $dbfriendlyname, $dbversion['version'], $okversion));
     }