MDL-32149 PHPUnit test support - part 2

Includes:
* constants refactoring
* reworked db table init
* support for $CFG->debug = -1
* functional DB tests
* fixed $DB->get_indexes() to not throw exceptions when table does not exist
* fix handling of user passwords in test db
* add debug info to exception messages
* removed unnecessary PHP debug errors from mathslib
* fixed @error suppression in get_string
* fixed PHPUnit error handler setup
* added timezone info to default install

admin/tool/phpunit/cli/util.php

@@ -29,7 +29,7 @@
  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 
-define('PHPUNIT_CLI_UTIL', true);
+define('PHPUNIT_UTIL', true);
 
 require(__DIR__ . '/../../../../lib/phpunit/bootstrap.php');
 require_once($CFG->libdir.'/phpunit/lib.php');