Added More Abi information.

Make Messages mirror clang Types better.
Added type size and alignments for independent and complete types.
Added vtable layout for CXXRecordDecls.
Added abi information for variables with global storage.
Added new return status to signify abi extension.
Added checks for access specifier downgrades.
Removed repeated code from header-abi-diff.

Test: header-abi-dumper -o example1.dump tests/input/example1.cpp -I
tests -- -x c++ -std=c++11 -I . -I
~/android/aosp/external/clang/lib/Headers

Change-Id: I21b5a8ef6dff92ecae47a0b1c46342862c5e0ebd