Php55

About 8df8c44 I think this one was already merged, can you please check.

About 5d100c7 We could probably improves things in master, for 5.4, but I don't have any build of PHP with system gd (only debian use it, AFAIK).

With PHP 5.5, most of GD feature are in sync with bundled / system libgd.
This is the only not supported function.

So, I think, handling this for php 5.5 only is acceptable.