cpp11-migrate: Add option to detect and use macros that expand to 'override'

Added a new option -override-macros which causes the, the add-override
transform to detect macros that expand to 'override' (like LLVM_OVERRIDE) and
use these macros instead of the override keyword directly.



git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@183001 91177308-0d34-0410-b5e6-96231b3b80d8