Merge from trunk r51234-r51251

* Revert "zer000"'s Cycles test node commits. (r47479 and 47556)
* Some cleanup to smoke code.

Merging revisions 51077-51234 from trunk

Merge with trunk r51077

Merge with trunk r50245 + fixed issues caused by previous (failed?) merge.

svn merge ^/trunk/blender -r50097:50211

minor changes needed for building with smoke disabled

svn merge ^/trunk/blender -r49776:50097

Fix: Smoke flow texture used UV maps incorrectly. (Double size)

* Some improvements to fire simulation code.
* It's now possible to set "flame rate" higher than 1.0. Higher rate basically means taller flame.
* More tweaking to "Quick Smoke" operator settings. Fire material is now also added by default even for smoke preset. -> You can now use quick smoke to easily setup a basic render settings that cover colored smoke and fire.
* Added settings to use a texture to define smoke flow "strength" for mesh emission. You can use automatically generated coordinates or UV layer.
* Fix: Adaptive domain bounds weren't drawn at all if smoke was uninitialized.
* Code cleanup.

Merge with trunk r49776

* Fix: smoke collision velocity got messed up if domain was moved during simulation.
* Fixed possible crash when changing smoke collision type.
* Fix: Viewport preview of high resolution smoke was drawn with too low density.

Two fixes for domain boundary conditions.
* Domain vertical velocity was accelerating over time. This issue has been in trunk since smoke was first introduced, but was especially troublesome for fire simulations due to higher temperatures and therefore higher buoyancy lift.
* Domain sides were partly considered obstacles regardless of the active "Border Collisions" setting. Now all boundaries behave identically. This should be especially useful when using new gsoc features like domain rotation or changing gravity direction.

Merge with trunk r49600

* Active simulation fields are now set dynamically based on simulation content.
- For example fire related data/simulation is only processed when there is a fire type brush affecting the domain. Color data is enabled only when multiple colors are needed.
- This way most simulations require less disk space and are faster to calculate compared to previous branch versions.
* Tweaked smoke 3D-view shader to match previous non-colored version.
* Fixed memory leak with smoke colors.

* Added colors to smoke simulations. You can select smoke color for flows and for smoke emitted from fire.
* Added color support to smoke 3D-view preview.
* Added color support to Blender Internal "Voxel Data" textures. To render smoke with colors also enable "Reflection Color" from texture settings.
* Added options to disable heat, fire and colors from simulations. I'm going to make this automatic during next week, but until then you can use these settings for additional speedup if you don't need certain parts of simulation.
* Fix: It wasn't possible to select "Domain Object" for smoke force field from same object.
* Fix: Force fields affected smoke incorrectly when using adaptive domain.
* Fix: Smoke initial velocity sometimes got messed up for first frame.
* Fix: Smoke initial velocity was applied incorrectly in some cases.
* Some code cleanup and refactoring.

Merge with trunk r49076

* Fix: Emitting smoke from particles didn't work after last commit.
* "Map to Bounds" is now enabled by default for new textures. One less thing to worry about when rendering adaptive domain. :p

Added a new force field type: "Smoke Flow".

It applies smoke simulation air flow velocity as a force to other Blender simulations that use force fields. To use it you need to add a "Smoke Flow" force field and select domain object for it.

To get an idea of what this is about, here is a video of it being used on particles: https://www.youtube.com/watch?v=lqRIxVQuVno

Merge with trunk r48602