Retrieve last frame rgb data (gl, vk, dx9, dx11).
Specific save screenshot code for android, iOS and UWP.
Add Save Screenshot emu key (F12 by default)
vk: defer deletion of in-flight textures when texture cache is cleared.
vk: fix issue when updating imgui textures after a render pass has begun
(achievements)
vk: palette texture not updated after a state has been loaded.
gl: Move opengl-specific stuff into opengl imgui driver.
savestate: Add non compressed header, following by screenshot png data,
before actual savestate.
Issue #842
Flyinghead