llvm-pdbdump: Only dump whitelisted global symbols.

llvm-pdbdump: Only dump whitelisted global symbols.

Dumping the global scope contains a lot of very uninteresting
things and is generally polluted with a lot of random junk.
Furthermore, it dumps values unsorted, making it hard to read.
This patch dumps known interesting types only, and as a side
effect sorts the list by symbol type.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@229232 91177308-0d34-0410-b5e6-96231b3b80d8