Issue #2365929: Include xautoload.module from xautoload.install.

Drupal 7 attempts to always include the *.module file before the *.install file, but it sometimes fails to do so.
One case where this happens is if xautoload is automatically downloaded as a dependency with drush en -y MODULENAME.
See https://www.drupal.org/node/2228825#comment-9148123
Issue #2365781: DEBUG_BACKTRACE_IGNORE_ARGS is not available in PHP < 5.3.6.
Fixes https://www.drupal.org/node/2365781
Issue #2355259: Add empty constructor in LibrariesInfoAlter, to avoid the librariesInfoAlter() method to be used as a constructor fallback.