_kernel_unwind now understands SFMFD instructions in function entry.
Kevin Bracey authored
It also copes with STFE now - it was totally broken.
32-bit stubs and corresponding LibInit SWIs created.
All rather untested.

Version 4.97, 4.12.2.3. Tagged as 'RISC_OSLib-4_97-4_12_2_3'
2b278303