OpenGL2: Remove and force r_softOverbright.
Replace deprecated alDopplerVelocity with alSpeedOfSound per OpenAL 1.1 spec
Remove references to alDopplerVelocity

Let's load driver even if it doesn't have the deprecated alDopplerVelocity.
OpenGL2: Fix pshadows for MDR models
Fix native trap_BotMutateGoalFuzzyLogic
Fix s_alDopplerSpeed default value
OpenGL2: Minor GLSL shader improvements.
OpenGL2: Add normalScale and parallaxDepth stage keywords and helper cvars.
OpenGL2: Set default normal/specular in RE_RegisterShaderFromImage
Merge pull request #57 from MAN-AT-ARMS/specularScale

OpenGL2: Set default normal/specular in RE_RegisterShaderFromImage
Don't wash out HDR vertex lite surfaces in OpenGL2

Vertex lite surfaces being brighter than light maps looks bad,
they're meant to look the same. Especially in ET, which mixes
them fequently. It's noticeable in Q3 too though.

BSP lightmaps (i.e. not external HDR lightmaps) use
R_ColorShiftLightingBytes, now *Floats (used by vertex colors)
has the same behavior.

This may be a problem for HDR lightmaps, as the RGB will always be
scaled to 0.0 to 1.0 range.

I had enabled this for non-HDR before, but now HDR needs it too.
Merge branch 'master' into sdl2
Update SDL2 to 2.0.2