Add feature to cache ISOs in RAM to avoid I/O stutters. 64-bit only. Loading gets slow though.

TODO: Make it cache in the background on load. Allow on 32-bit for small ISOs.
D3D: Reduce logspam
Buildfix (needed an include in the header on some platforms so let's move to the cpp file)
Always clamp in ToRGB[A]?().

Before we only clamped with SSE, better to be consistent.  This may also
be slightly faster.
Missing include for Linux/etc.
And fix an issue building on Android.
Merge pull request #7035 from unknownbrackets/gpu-minor

Always clamp in ToRGB[A]?()