nginx: each module's distfile name should include the name of the module

[ryandesign (Ryan Carsten Schmidt)]

We currently have the terrible situation in the nginx port where there are a zillion modules in variants, but each module has a separate distfile and its filename is just its version number and extension. This obviously makes it impossible for anyone browsing the ​directory listing to know which version goes with which module and it was inevitable that there would eventually be a version conflict, which has now happened and one module's distfile name had to be changed (to a name without any extension at all??) to avoid colliding with another module's existing distfile.

Alternately and preferably, move each module to its own port and use the github portgroup which will take care of the distfile names for you.