New crosscompile script for creating linux packages is working now

Benefits of new approach:
* No root prevelegies required
* Allows to build from current working tree
* No need to create full package to test modifications
* Allows to build with custom library set, without affecting system libraries
* Easy to debug the application because dependent libraries can also provide debug symbols
Allow Windows Users to use MyPaint brushes
Add Lossless H.264 encoding profile. The resulting file is compatible with Sony Vegas and other software based on QuickTime AVC decoders.
Allow target to handle alpha in 4 different ways
Allow to render alpha information into separate file (GUI).

This is useful for rendering into formats that doesn't support alpha channel (avi, jpeg, etc).
In this case user can selec "Extract Alpha" option in rendering dialog and alpha information will be rendered into separate file.
Allow to render alpha information into separate file (CLI).

The new option "--extract-alpha" (or "-x") allows to extract alpha information into separate file ("-alpha" suffix added into output filename).
Linux build: Add possibility to build 32bit packages on 64bit host.

With this change the new Linux build script now completely replaces old one.
PNG target now properly responding to "Extract alpha" option
OSX build: It is safe to revert 7a87974c now (MacPorts issue #42434 is fixed)
OSX build: Change configuration to build without X11
New icons

Jack, Sound Layer, Switch Layer, and Brush Tool icons.
OSX build: Use Clearlooks Gtk theme
Increase default bitrate for ffmpeg target
Fix #138: Allow to use 'avconv' binary instead of 'ffmpeg'
Use Lossless H.264 codec by default for FFmpeg encoding
Cygwin build: Fix architecture condition
Typo
Fix FFmpeg options - now compatible with avconv
Fix permissions for 64-bit DEB package
Fix #652: Zoom widget dissapeared form Preview Window