Allow hyphens in cdylib names

[pbor]

hypens are currently allowed in binaries, but not allowed in libraries: #1443

It would be great if cdylibs could be treated like binaries, since for that case it is sometimes important to have control of the resulting filename.

In particular when trying to replace an existing .so with a rust implementation, you need to be able to generate the same filename expected by the programs loading the library.