Several cleanups to the buildsystem:
 - Do better factoring of common libs between platforms.
 - Add support to building on Windows.
 - Remove Qt4 support.
 - Re-sort file lists and add missing headers.

This should fix the GL loading errors that occur in some drivers due to
the use of deprecated functions by GLEW. Side benefits are more accurate
auto-completion (deprecated function and symbols don't exist) and faster
pointer loading (less entrypoints to load). In addition it removes an
external library depency, simplifying the build system a bit and
eliminating one set of binary libraries for Windows.

Screen contents are now displayed using textured quads. This can be updated to expose an FBO once an OpenGL backend for when Pica rendering is being worked on. That FBO's texture can then be applied to the quads.

Previously, FBO blitting was used in order to display screen contents, which did not work on OS X. The new textured quad approach is less of a compatibility risk.

Pica/Math: Improved the design of the Vec2/Vec3/Vec4 classes and simplified rasterizer code accordingly.

- Swizzlers now return const objects so that things like "first_vec4.xyz() = some_vec3" now will fail to compile (ideally we should support some vector holding references to make this actually work).
- The methods "InsertBeforeX/Y/Z" and "Append" have been replaced by more versions of MakeVec, which now also supports building new vectors from vectors.
- Vector library now follows C++ type promotion rules (hence, the result of Vec2<u8> with another Vec2<u8> is now a Vec2<int>).

Pica/citra-qt: Replace command list view and command list debugging code with something more sophisticated.

Connect the emu_thread start/finish to a moveContext slot.

Fixes building with clang.

24-bit floating points are used internally for calculations on the GPU, however the current code will still emulate that with 32-bit floating points.
In the future we might want to accurately perform the calculations with correct bitness in the future, but for now we just wrap the calculations around this class.

I wrote most of this for ppsspp, so I hold full copyright over it.
In addition to the original release in ppsspp, this provides functionality to easily extend e.g. two-dimensional vectors to three-dimensional vectors.