[llvm-pdbdump] Display full enum definitions.

[llvm-pdbdump] Display full enum definitions.

This will now display enum definitions both at the global
scope as well as nested inside of classes.  Additionally,
it will no longer display enums at the global scope if the
enum is nested.  Instead, it will omit the definition of
the enum globally and instead emit it in the corresponding
class definition.

llvm-svn: 231215