More fixes for crankshaft bring-up:

- Since PPC has no efficient method of doing pc-relative loads,
  disable use of the deopt_jump_table in favor of generating direct branches
  in DeoptimizeIf.

- Implement primitive support in MacroAssembler::Jump for conditions
  and RelocInfo::RUNTIME_ENTRY.

- Fix LCoddeGen::DoAddI to correctly handle overflow.