This commit:
* Adds a new subproject, audio_core.
* Defines structures that exist in DSP shared memory.
* Hooks up various other parts of the emulator into audio core.
This sets the foundation for a later HLE DSP implementation.
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.
