Fix one sceHeap func, add reporting.
Savestate the exit callback, reporting.

Seems like LoadExecForUser_362A956B() uses it, so we need to save it.
I have no confidence that function works correctly, so let's report it.
Cleanup sceKernelRegisterExitCallback() per tests.
Merge pull request #3976 from unknownbrackets/minor

Small reporting / exit callback changes