Code review comment for lp:~adeuring/launchpad/bug-172507

This branch changes the icon shown for download links of patches in bug pages (bug 172507).

The change is quite straightforward.

  - the file lib/canonical/launchpad/icing/icon-sprites-3 is "extended" with the new icon
  - a new CSS class "haspatch-icon" for the position of the new icon in icon-sprites-3
  - CSS class used for download links in the "patches" portlet

The diff is ridicuosly long because i added also the SVG file for the patch icon.

tests: None

screenshot: http://people.canonical.com/~adeuring/patch-icons.png

= Launchpad lint =

Checking for conflicts. and issues in doctests and templates.
Running jslint, xmllint, pyflakes, and pylint.
Using normal rules.

Linting changed files:
  lib/canonical/launchpad/icing/icon-sprites-3
  lib/canonical/launchpad/icing/style-3-0.css
  lib/canonical/launchpad/icing-sources/haspatch.svg
  lib/lp/bugs/templates/bug-portlet-attachments.pt