Getting the baked-in .pdb location from an assembly with Mono.Cecil 0.9.4

Because it isn't always as simple as

as is done in Mono.Cecil.Pdb.PdbHelper, if assemblies and symbols have been moved to separate locations during a build.

The tools are there -- we just need to get the debug data from the PE image if it's present, skip the first 24 bytes, and interpret the rest as a string. Alas, all the are annoyingly just slightly encapsulated from us. But never mind! Reflection gets us there without having to negotiate a patch or make a fork: