Renamed drupal_uninstall_modules() to module_uninstall()

The function drupal_uninstall_modules() was renamed to module_uninstall() and moved from core/includes/install.inc to core/includes/module.inc. The usage is unchanged.

Example code:

// Drupal 7
// Uninstall Comment module.
drupal_uninstall_modules(array('comment'));

// Drupal 8
// Uninstall Comment module.
module_uninstall(array('comment'));