Refactor|Map Renderer: Sector light level and color as draw state properties
Merge branch 'master' into revise-map-geometry-generation
Refactor: Updated more map renderer internal APIs to use libdeng2's Vector
Refactor|Map Renderer: Further cleanup of wall section light level smoothing algorithm
Refactor|Map Renderer: Began separating render logic from geometry construction

I'll try to document and clean things up as I go...
Refactor|Map Renderer: Moved more logic into wallSectionLightLevelDeltas()
Refactor|Map Renderer: Turned the writeWallSection() function stack into a linear process
Refactor|Map Renderer: Moved HEdge::prepareWallDivs() to rend_main.cpp

In its present form this data and the associated logics are firmly a
part of the render domain.

Also removed many unnecessary header includes.
Refactor|Map Renderer: Reworked WallDivs into a C++ class
Map Renderer: Began remodeling wall geometry construction

Transitioning to an edge-centric model.
Map Renderer: Cleanup
Map Renderer|SectionEdge: SectionEdge can now be used for Polyobj sections also
Map Renderer|Refactor: Consolidated more wall geometry construction logic
SectionEdge: Minor API improvements
HEdge: Moved wallSectionSectors() logic into HEdge

Plus a wall section draw state optimization.
Map Renderer|Refactor: Consolidated more map geometry construction logic
Map Renderer|Refactor: Apply the near-fade logic for wall sections in writeWallSection()
Map Renderer|Refactor: Further cleaned up writeWallSection()
SectionEdge: The class user must handle the degenerate case (top < bottom)

Note that top == bottom is not degenerate and is supported, however.

It remains to be seen whether this is semantically the right approach
for this class. We'll know for sure once the WallDivs implementation
has been revised.
Refactor|Map Renderer: Disentangling writeWallSections2Twosided's "solid segment" logic...