String(named) keys for $requirements array returned by hook_requirement()

Hi there,

while writing a feature to check for needed drupal requirements within drush_nagios,
i discovered, that $requirements are not strings like in other modules like e.g. 'unicode' and 'cron' from core, 'xmlsitemap_generated' from xmlsitemap...

Though that would be awesome and more compliant to get this implemented.

Regards