- Refactor the code that resolve basic block references to a TargetJITInfo

  method.
- Added synchronizeICache() to TargetJITInfo. It is called after each block
  of code is emitted to flush the icache. This ensures correct execution
  on targets that have separate dcache and icache.
- Added PPC / Mac OS X specific code to do icache flushing.

llvm-svn: 29276