Enable most optimizations with loops

Summary: Currently disables refcount-opts and reoptimize for regions that have
loops. This is controlled by a new field in IRBuilder, which should go
away once those two passes are fixed.

Reviewed By: @ottoni

Differential Revision: D1484156
Add test for gmp ignoring base for hex-like strings

Summary: Found by intermitently-failing mediawiki test

Reviewed By: @LiraNuna

Differential Revision: D1488998
Updated the drupal framework tests to 8.0-alpha13

Summary: This uncovers one error:
```
1) Drupal\Tests\Core\Config\Entity\ConfigEntityBaseUnitTest::testSort

RUN TEST FILE:  cd /root/hhvm/hphp/test/frameworks/framework_downloads/drupal/core && /root/hhvm/hphp/test/frameworks/../../hhvm/hhvm -v Repo.Local.Mode=-- -v Repo.Central.Path=/tmp/framework-testDgjSb2 --config /root/hhvm/hphp/test/frameworks/php.ini -c /root/hhvm/hphp/test/frameworks/.generated.php.ini /root/hhvm/hphp/test/frameworks/vendor/bin/phpunit --debug  -c /root/hhvm/hphp/test/frameworks/framework_downloads/drupal/core/phpunit.xml.dist --filter 'Drupal\\Tests\\Core\\Config\\Entity\\ConfigEntityBaseUnitTest::testSort'

Failed asserting that two variables reference the same object.

/root/hhvm/hphp/test/frameworks/framework_downloads/drupal/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityBaseUnitTest.php:432
/root/hhvm/hphp/test/frameworks/vendor/phpunit/phpunit/src/TextUI/Command.php:179
/root/hhvm/hphp/test/frameworks/vendor/phpunit/phpunit/src/TextUI/Command.php:132
```
Closes https://github.com/facebook/hhvm/pull/3373

Reviewed By: @ptarjan

Differential Revision: D1487081