[llvm-pdbdump] Support dynamic load address and external symbols.

[llvm-pdbdump] Support dynamic load address and external symbols.

This patch adds the --load-address command line option to
llvm-pdbdump, which dumps all addresses assuming the module has
loaded at the specified address.

Additionally, this patch adds an option to llvm-pdbdump to support
dumping of public symbols (i.e. symbols with external linkage).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@236342 91177308-0d34-0410-b5e6-96231b3b80d8