Fixes for runqemu script and OVMF recipe (with suggestions incorporated)

This series fixes:  
* Blank screen when using runqemu with the OVMF firmware (albiet in a somewhat hacky way)  
* OVMF recipe not warning the user if compiled for unsupported architectures like MIPS  
* OVMF recipe never creating 32-bit firmware, even when it should  

It also upgrades OVMF to a newer upstream version, which fixes an upstream bug that caused build failures with GCC 4.9.