[PATCH] Fix return sequence on armv4 thumb

[Tim Northover]

> I had a read on the old APCS and couldn't find any mentions and to why R3 should be used as a return register (though it says R0~R3 can be used for returning values). But since we don't follow the APCS any more, even on ARMv4T, I think we should discard any reference to that document.

iOS is unfortunately stuck with the APCS.

Cheers.

Tim.

http://reviews.llvm.org/D4748