Fix older savestates no longer loading.
Move DXT decoding to GPU/Common/.
Move some texture deindexing to GPU/Common/.
Add a way to get to the current texture as well.
Add a preview for the current texture as well.
Show alpha in textures in the GE debugger.
Add a separate button to step by op/cmd.
Ignore framebuffer alpha in preview, often 0.
Shutdown cleanly even when GE debugger is paused.
Listen for shutdown in thread loops.

This way we don't need to use wait_for(), much better.
Also because there are slightly more correct cond vars on win32.
Merge pull request #3952 from unknownbrackets/debugger

Show a texture preview in addition to the framebuffer preview