Change PSPPointer function name Valid to IsValid.

Improves readability and shows intent better.
Fix some signed/unsigned mismatch warnings in __sceAudio.cpp.
Merge pull request #2464 from lioncash/master

Change PSPPointer function name Valid to IsValid. Also fix some signed/unsigned mismatch warnings in __sceAudio.cpp
Merge remote-tracking branch 'upstream/master' into framebuffers-to-mem
Add FramebuffersToMem option to allow disabling of reading framebuffer contents to memory (defaults to false).