Assembler:

Peephole optimiser:
- Could e.g. turn "ldr lr,[sp,#OFF]; mov pc,lr"
  into "ldr pc,[sp#OFF]", but then the LR save slot must
  be in the caller's frame not the callee's.
- Also kill "mov r0,r0" which seems to occur often.

hipe_arm:
- Handle more non-trivial immediates in mk_li/mk_load/mk_store.
  See e.g. big_list, which has many 11-bit character constants.

Floating point:
- Drop no_inline_fp. Implement FP ops as calls to C or ASM
  primops. All FP values passed by reference in memory.
  This should at least reduce consing costs.

Linear scan:
- Do not hardcode temp1/temp2/temp3. Instead just take three
  regs from (All\Fixed)\Params. (Ditto in PowerPC.)
