More SPU Instructions: Floating point comparison

* Implemented Floating/Double-floating comparison instructions:
FCGT, FCMGT, FCEQ, FCMEQ, DFCGT, DFCMGT, DFCEQ, DFCMEQ

* Implemented more Floating/Double-floating operations:
FMA, FMS, FNMS, DFMA, DFMS, DFNMS, DFNMA

* Implemented Double / Single floating-point conversion:
FESD, FRSD