Qt: Buildfix ffmpeg search
Cut down on cached booleans for non-softgpu things.
Add a config option for the slow framebuf effects.

Like cluts, blitting, etc.  At higher render resolutions these are
expensive, and on some mobile devices they may be too much.

Of course, they're only used when needed so this is a speedhack.
Show option to disable framebuf effects in UI.
Merge pull request #6527 from unknownbrackets/fb-slow-option

Add an option to disable clut/render-to-self/etc.
Don't crash when framebuffer is a nullptr.
Merge pull request #6530 from thedax/tex-cache-crashfix

Don't crash when framebuffer is a nullptr.
Change default of "disable slow framebuf effects" to false