Skip style sheets with print media

I have completely different symptoms which stem from the same problem.

In the mimemail.module file, the template_preprocess_mimemail_message() function adds style information to the email by taking the output of drupal_get_css() and concatenating the contents of all the linked stylesheets within a single <style>...</style> tag.

Unfortunately, in doing so, mimemail is stripping the "media=" selector from each link, so that styles intended for printing are mixed with styles intended for screen display.

In my case, this resulted in my print.css stylesheet, which hides selected portions of the page for printing, also hiding certain portions of the Yahoo webmail API when their customers view my messages.

The fix is to replace each link by an embedded stylesheet, one-by-one, while retaining the "media=" selector.

I am attaching three patches, one to fix the css errors, one to fix various E_ALL warnings, and one to fix a mail_alter bug reported in #448996: Wrong implementation of hook_mail_alter().

I have also corrected some unrelated problems in the original code:

1. The test for file_exists($styles) is made before the $styles variable is defined.
2. The regex patterns should keep working if drupal_get_css() changes how it formats its output.
3. Whitespace is collapsed rather than stripped. See #448670: Spaces and Line Breaks are removed from CSS definitions.
4. I also found it necessary to add linefeeds. Otherwise, my /usr/sbin/sendmail chokes whenever a single line exceeds 5000 characters.

I think it's better (less drastic modification at least) if we just remove the lines which have print media type.

I agree with sgabe in #3, less of an impact to just skip the print styles.
Please note: in sgabe's patch, the line reading

+ $styles = preg_replace($pattern, $replaces, drupal_get_css());

should be

+ $styles = preg_replace($patterns, $replaces, drupal_get_css());

($patterns instead of $pattern).
[Additional note: I see sgabe has corrected it in the patch on http://drupal.org/node/743150 ]

@gjvoosten: Yeah, I forgot to attach the right patch. Thanks for noticing.

I am attaching a patch with another approach, posted by AlexisWilke in #870568: CSS concatenation problems & solution.

Please ignore the previous patch...

I think we should use CSS files with theme type only.

This patch works fine, even if it does not apply cleanly anymore.
I'm ready to make it clean again for both 6.x and 7.x, it's quite a major thing for everyone who has fine-grained print.css, but does not need a completely different mail.css

Changing version.

Committed to both branches.