[analyzer] Add an abstraction for the bit width and signedness of an APSInt. No functionality change.

There are more parts of the analyzer that could use the convenience of APSIntType, particularly the constraint engine, but that needs a fair amount of rewriting to handle mixed-type constraints anyway.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@156360 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed