The old system of just defining macros available in some other platform
was susceptible to silently using the wrong code if you forgot to
include a particular header. This fixes a crash on non-Windows platforms
introduced by e1fbac3c.

More cleanups

GPU: Implemented default vertex shader attributes.

Fixes some games crashing.

HLE: Clean up SVC dispatch mechanism

Core: Remove some unused functions and types

Rename git submodules, so they are more easily accessible from external tools

EmuWindow: Clip mouse input coordinates to emulated screen dimensions.

If the mouse position for a mouse move/drag would take it outside the emulated screen dimensions, clip the coordinates to
the emulated screen dimensions.
Qt and GLFW will report negative coordinates for mouse positions to the left, or above citra window. Added restriction
to mouse coordinates passed to touchmoved by Qt/GLFW to be greater or equal to zero.

Fix emulation state resetting to support multiple emulation sessions