Dropping support for PHP 5.3

Bug 1576448. As discussed at the 52nd Mahara developer meeting.

behatnotneeded: Can't test in Behat (requires environmental
changes.)

Change-Id: I6cdfb0c154077f597128b7c3c1fd86b40b36c772

README.md

@@ -64,7 +64,7 @@ modification to support other databases.
 
 ### PHP
 
-Mahara requires PHP version 5.3 or later. The "magic_quotes" and "register_globals"
+Mahara requires PHP version 5.4 or later. The "magic_quotes" and "register_globals"
 settings should be turned *off* (which is the default on modern PHP installations).
 
 The following PHP extensions are also required:

htdocs/lib/mahara.php

@@ -19,7 +19,7 @@ defined('INTERNAL') || die();
 function ensure_sanity() {
 
     // PHP version
-    $phpversionrequired = '5.3.0';
+    $phpversionrequired = '5.4.0';
     if (version_compare(phpversion(), $phpversionrequired) < 0) {
         throw new ConfigSanityException(get_string('phpversion', 'error', $phpversionrequired));
     }