Fix compilation error caused by inline functions

[omarocegueda]

If inline functions are just declared in the pxd, cython attempts to declare inline pointers to them, which is invalid since variables cannot be declared inline. According to this:
http://docs.cython.org/src/tutorial/pxd_files.html
inline functions should be defined, not just declared in the pxd.
Unfortunately, right now I don't have access to the buildbots to try this, but in theory this should fix the issue.

[arokem]

Yup. I can confirm that with this branch in place everything compiles just fine on my (Mac) laptop, and tests all pass (except for the one that should be taken care of once #612 lands).

[arokem]

I am going to go ahead and merge this into master, since it's small and presumably fixes a current breakage. Let's see what the buildbots do with this.

[omarocegueda]

Thanks Ariel! =D