setup.py: dependency checking does not ignore comments

[Mike Hansen]

*

Hello,

reading the code, I see another problem if ones has the following line in its .pyx:

cimport mod#mycomment

I such a case, we'll look for a dependency mod#mycomment.pxd instead of mod.pxd.

Otherwise, the patch solves the aforementioned problems.

Cheers

[Craig Citro]

This is a dupe of #5104.