MinGW build: Ignore symlinks
Fix vertical mouse scroll event for timetrack
Fix rendering for boolean parameters
Use pref unit system for Spline(bline) tool option panel
Use pref unit system for some tools.

Including circle, draw, polygon, rectangle, star and width tools.
There are some other options which should use distance widget and
their unit should be inherit from setup dialog (user preferences).
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
Merge https://github.com/morevnaproject/synfig into gtk-3
Add parameters to set position and resolution of transformation grid
Layers created via "Layer->New Layer" had wrong opacity. Fixed now.
Merge branch 'gtk3' of https://github.com/morevnaproject/synfig into gtk-3