[Bug] Usage of internal glibc header sys/cdefs.h

Trying to compile Julia on a musl libc system reveals this bug on openlibm.
As instructed by musl libc documentation, I'm reporting the bug.

[tkelman]

Ah, I think this has already been fixed in 9a48c87, but Julia's still using a version of openlibm that's a little over a year old. We would need to test upgrading to latest master carefully on all platforms, since some functions were removed here that Julia might have actually needed.

[yuyichao]

since some functions were removed here that Julia might have actually needed.

They should be added back now. Julia with openlibm git master passes all tests on linux.

Nice!

Julia with openlibm git master passes all tests on linux.

Can Julia start using the newest openlibm then?

[tkelman]

ref #85 (comment) and JuliaLang/julia#13868

edit: ah, the single precision bessel got put back in c29e8b1