Update for ARM-M0 model and tools.

The model inadvertently supported B.W instructions, which aren't found in M0.

Also fixes a problem with the evaluation of POP instructions.
Update for MIPS model and tools.

Simplifies handling of load/stores. (The tools now no longer attempt to accommodate reverse endian mode.)

Fixes modelling of exceptions occurring for an instruction in the branch delay slot. (This has to be properly processed and flagged using the component CP0.Cause.BD.)

Also fixed errors in the specifications of the MADD, MADDU, MSUB, MSUBU, SWR and SDR instructions. (Thanks to Mike Roe for testing the model.)