Update libc headers to use musl headers.
Fix test_zlib. off_t is now 64bit.
Update to work with new libc headers.
Fix other.test_embind & other.test_static_link.
Fix time tests.
Add __va_copy as a compat/stdarg.h
Fix fpclassify with musl libc headers.

musl defines __fpclassify, __fpclassifyf, __fpclassifyl while
the old headers used __fpclassifyd for double rather than
__fpclassify.
Fix seekdir() for 64-bit off_t.
Fix ftello() for 64 bit off_t return value.
Provide better impl of __assert_fail().
Bump version for new libc headers.
Emscripten requires different #s for stdio fds.
Handle fpclassify and signbit for long double.
Fix sockaddr struct definitions for musl.
gethostbyname_r update.

* gethostbyname_r is now the 6 arg version.
* Make enet use the right code path (this should be upstreamed).
* Add a compat header to make these declarations visible to all without
  extra compilation flags.