TINYGL: Added external interface for tglBlendFunc
TINYGL: Encapsulated pixel access in FrameBuffer class, provided an implementation of glBlendFunc.
TINYGL: Implemented alpha interpolation in triangle rasterization routine.
MYST3: Add support for the sweeping counter
MYST3: Fix the variable not in range opcode logic
MYST3: Add support for movies with additive blending

This is used in LIFO 66
TINYGL: Implemented alpha blending and color transformation in sprite blitting for Grim TinyGL renderer.
TINYGL: Modified changelog.
Merge pull request #937 from subr3v/glBlend-implementation

TINYGL: glBlendFunc Implementation
ALL: sync with ScummVM
GRAPHICS: Refactoring

Rename some variables and functions of the graphics drivers to distinguish properly betwen textures and materials.
EMI: Implement screenshot thumbnails for savegames