Fix T4199: Knife holes in concave ngons failed

BM_face_point_inside_test assumed the face center was inside the face.
Fix T42074, textured lamps influncing other layers

The solution is to do the multiplication with the energy in the shader
after texture application.

We might be able to avoid setting dyncol completely, but this needs
better investigation. Some shader paths also look a bit redundant.

Also, texture mapping is not supported very well for light lamps, might
also need investigation.
Cleanup to previous commit, we can reuse set_rgb instead of new function
Fix T41957: Shadow color texture mapping was using wrong factor
Cleanup: use bool
Cleanup: redundant casts
Allow render engine to declare whether it's capable of the texture rendering or not

If render engine has bl_use_texture_preview set to truth blender wouldn't fallback to
the blender internal rendering for previews.
Fix T42106: Box image mapping shows black triangles if they point to a corner and blend is 0

After discussion with cambo here we decided it's better to choose arbitrary side of the box
(in this case it's X-axis) and use image from it. That's better than doing a blackness.

P.S. This is literally a corner case anyway.
Call python3 explicitly from tgz util
Icons: were relicensed to GPL2+ metadata was CC-NC
Partial fix of T42052: Clip editor does not support Continue zoom style
Paint: add debug print to time strokes
Sculpt: dyntopo, avoid redundant gset remove calls
Cleanup: use bool
Sculpt: minor speedup for dyntopo

Add retake to range-tree to avoid double lookup.
Ghost Context Refactor
https://developer.blender.org/D643
Separates graphics context creation from window code in Ghost so that they can vary separately.
We need libglewmx too, now.
Fix bplayer linking after recent addition of glew_mx.
Fix T42137: Keymap editing is broken

Own mistake in previous fix here, was too greedy in finding an existing kmi of UserPref add diff kmi, we only want
to ignore exact same kmi's here.
OSX: adapt fs_menue to modern entries handling