Reduce sceMpegRingbufferAvailableSize() logspam.

It's really mostly interesting when it changes only.
Switch to a 64-bit function hash.
Attempt to prevent shutdown crash in debugger.
Add memchecks for common HLE copy operations.

Better to catch some than miss everything.
Merge pull request #4830 from unknownbrackets/debugger

Switch to 64-bit hash, minor debugger stuff