Add support for dumping debug tables to llvm-pdbdump.

PDB stores some of its data in streams and some in tables.
This patch teaches llvm-pdbdump to dump basic summary data
for the debug tables.

In support of this, this patch also adds some DIA helper
classes, such as a wrapper around an IDiaSymbol interface,
as well as helpers for outputting various enumerations to
a raw_ostream.

llvm-svn: 227257