[codeview] Share more enums across the writer and the dumper

Moves some .def files into include/DebugInfo/CodeView.

Aslo remove a 'using namespace' directive from a header in readobj and
update the uses of the endian helper types to compensate.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@257712 91177308-0d34-0410-b5e6-96231b3b80d8
8 files changed