Continuing work on ObjC tidyup:

- Moved the CGObjCRuntime functions out of CGObjCMac.cpp into CGObjCRuntime.cpp

- Added generic functions in CGObjCRuntime for emitting @try and @synchronize
  blocks, usable by any runtime that uses DWARF exceptions.

- Made the GNU runtimes use these functions.

It should now be possible to replace the equivalent functions in
CGObjCNonFragileABIMac with simple calls to these two functions, providing the
runtime functions as arguments.  I'll post a diff to the list for review before
making any changes to the Mac runtime stuff.

llvm-svn: 128274