CSS aggregation attempts to process @import in comment

When CSS aggregation is turned on, the @import declaration of CSS is handled and processed.

However, the string "@import" within a comment or an @import without the appropriate argument is not handled correctly.

How to reproduce:

• Add a css file to your style (or anywhere) with a comment like /* try this with @import */
  Turn on CSS aggregation
• Examine the resultant aggregation using firebug or whatever technique

What I expect: The comment to be intact, along with the rest of the file.

What happened instead: The file was truncated starting with where the @ was in @import (after 'with' in my example).

My opinion is that we'll not be able to resolve all problems like this until we actually parse CSS in order to compress and aggregate it. Until that point, all aggregation and compression is hacky.

See #494498: Add CSS parsing capability to Drupal concerning building a CSS parser into Drupal.