Avoid xinput pad jitter resetting axis state.

Should take care of #5526.
Qt: Optimisations for ARM desktop/tablet hosts.
Qt: Buildfix USING_GLES2 and not MOBILE_DEVICE
glBindFragDataLocation is not needed. Thanks HdkR.
Support fixed/fixed blending without a blit.
Convert blending to doubling in more cases.

We're not doubling the alpha, so all these cases are safe regardless of
the alpha value.
Support more src alpha doubling modes.

These prevent the need for more blits.
Reorganize alphablend state mapping logic.
Use shader blend for min/max when unsupported.
Merge pull request #6342 from unknownbrackets/xinput-fix

Avoid xinput pad jitter resetting axis state
Merge pull request #6350 from unknownbrackets/gpu-blend

Avoid blitting for a bunch of gpu blending modes
Disable vsync when exiting the game.

Not sure why, but with some drivers not doing this makes the process burn
cpu usage when back in the menu.  Fixes #6351.
Fixes #6353
Merge pull request #6355 from solarmystic/master

Fix #6353