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

- 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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@29276 91177308-0d34-0410-b5e6-96231b3b80d8