Upgrade to wcslib 4.25

Although now that I look, could we not add `WCSLIB_VERSION` as a constant in the Python wrapper for wcslib?  It's annoying that the value would be a float, but I dealt with that like this for CFITSIO:

https://github.com/astropy/astropy/blob/master/astropy/io/fits/src/compressionmodule.c#L1112

which works well enough where it matters (though IIRC CFITSIO has separate major and minor version macros now so I could probably update this...)