Cleanup includes, mostly in common

Loader: Fix format specifier warning

AppVeyor: Remove submodule checkout depth

This avoid intermittent build failures due to a commit not being
reachable using a fixed depth, at the expense of longer checkout times.

Implement blended downscaling for display transfers

Services/SOC: Added command headers to some of the soc commands.

vfp: Change return type of VFPInit from unsigned int to void.

vfp: Handle accesses to FPINST/FPINST2 system registers.

Also has a side-benefit of correcting access to the FPEXC register.

Remove unused type unions breaking aliasing rules in horrible ways

VideoCore: Fix Floating Point Warning

AppVeyor: Remove os: unstable

The default os has Qt now, so there no need for the unstable os.

Add helpers to create IPC command buffer headers and descriptors