astropy/astropy — pull request #2569 by embray (2014-05-27 18:31:20+00:00)
Title: Skip unnecessary copy of wcslib headers on each build.

As I reported [here](https://github.com/astropy/astropy-helpers/issues/19#issuecomment-44312018). Avoid copying the wcslib header files from cextern unnecessarily on each run of setup.py build. This will only copy them if they are missing/out of date.