Downgrade GLSL version to 1.50 (compatible with GL 3.2)
Merge pull request #81 from yuriks/downgrade-shader

Downgrade GLSL version to 1.50 (compatible with GL 3.2)
Remove virtual inheritance from RendererOpenGL

Also make destructor virtual so that instances are properly destructed.
[OpenGL] Shuffle initialization code around and rename functions.
Rename GPU::Regs::FramebufferFormat to PixelFormat

This name better represents what the enum does, and is less overloaded
in the context. (The whole register the enum is part of is also called
'format'.)
Introduce VAddr and PAddr typedefs for ARM addresses.
Rework OpenGL renderer.

The OpenGL renderer has been revised, with the following changes:
 - Initialization and rendering have been refactored to reduce the number of
   redundant objects used.
 - Framebuffer rotation is now done directly, using texture mapping.
 - Attempt to support the LCD framebuffer size registers, under the
   assumption that the 3DS hardware does hardware scaling in case they
   don't match the physical LCD resolution.
 - Vertex coordinates are now given in pixels, and the projection matrix
   isn't hardcoded anymore.