Ignore alpha when writing to display.
If __KernelLoadExec() fails, halt emulation.

Otherwise, we have no current thread, nothing can work.
sceKernelLoadExec(.../BOOT.BIN) loads EBOOT.BIN.

Fixes #2289, crash when pressing R+L+Start+Select in Final Fantasy 3.
Merge pull request #2296 from unknownbrackets/loadexec

sceKernelLoadExec(.../BOOT.BIN) should load EBOOT.BIN instead
Merge pull request #2292 from unknownbrackets/fbo-alpha

Ignore alpha when writing to display
Add support for external at3plus decoders on MacOSX 64bit.
Fix Blackberry10 building on non-Windows systems.
Hash/convert more when a CLU base is used.

This seems a bit strange, but the games that use these bases seem to read
outside the loaded CLUT to a previously loaded CLUT.

May cause a performance issue on games that use a base but don't do this.