Split ast frontend and ast processing.

Split into header-abi-dumper and header-abi-checker.
Removed dumping PCH.
TODO: Use protobuf instead.

Test: header-abi-dumper -o example1.dump tests/example1.h -- clang -x
c++ -I . -std=c++11.

Change-Id: I5b2aa8ab678843a57fddeeec929ac57c5a77ffc9
9 files changed