cleanup: style & tips
Fix T42420: Touchpad zoom and scroll gester using touchpad stopped working

Seems to be an own mistake on using Windows API.
CMake: correct own error using undefined var
World background working on cycle nodes.

This is added in the spirit of the general cycles GLSL system
which is pretty much WIP still.

This will only work on cycles at the moment but generating for blender
internal is possible too of course though it will be done in a separate
commit.

This hasn't been tested with all and every node in cycles, but
environment and regular textures with texture coordinates work.

There is some difference between the way cycles treats some coordinates,
which is in world space and the way GLSL treats them, which is in view
space.
We might want to explore and improve this further in the future.

...also </drumroll>
Freestyle: Fix for view map caching not flashed properly in view port rendering.
cmake/windows Change python installation so it does not trigger on simple rebuilds
Fix GLSL drawing of math absolute node.

Patch by Romanov Alexander of blen4web team!

Differential: D842

Thanks for the patch!
Do not use mipmapping on envmaps, can cause discontinuities on
environmental mapping when crossing the seam boundary.

Also output our favourite magenda on missing texture.
Fix for walk navigation not working with stereo camera (multiview)

Reviewers: campbellbarton

Differential Revision: https://developer.blender.org/D917
API Docs: remove hardcoded self from shellscript
Fix own commit: broke add background image
Transform: correct flag -> bool
Transform: fix for fcurve transform crash

counting handles was out of sync, now use exact same logic.
Fix T42653, solidify modifier not displaying correctly under edit mode.

Basically, our drawing code assumed we always use the edit mesh
materials, which can be different from the derived mesh
materials in modifiers doing overrides. We usually we want to use the
derived mesh when it is available instead.

There are two fixes here for both solid and textured mode. Unfortunately
the fixes do not help to make the display code less labyrinthian but I
expect this "should work" (tm and famous last words)

Solid mode fix is 95% from Bastien, thanks!
Addition/correction to previous commit:

subsurf needs the same modifications in its derived mesh function or
materials don't get updated at all anymore.
Partial Fix T42652: Transform falloff for mesh islands

This doesn't currently do anything clever when a single vertex is shared by multiple islands
(uses closest only).
Cleanup: duplicate headers
Fix graph editor rename button resetting focus when escaping from it.
This is a copy of what the outliner does and seems to work.
Cycles: Code cleanup, remove dead code
Cycles: Only report exporting curves if there are particle systems on the object