I did this on OS X 10.10.5 (14F27) using the OS X 10.10 SDK included in
Xcode 6.4 (6E35b) for syscall numbers. I believe this SDK is intended
for 64-bit Macs, but the syscall numbers aren't likely to vary. See also
the discussion in this thread:

    https://groups.google.com/d/topic/golang-dev/738LXeykFsM/discussion

This commit contains the same SYS_SYSCTL -> SYS___SYSCTL workaround
found in commit 9ef4b6c1; see its description for more info.

Change-Id: I952ae56032033b49f8910281c68dcc72abb2d106
Reviewed-on: https://go-review.googlesource.com/14151Reviewed-by: Ian Lance Taylor <iant@golang.org>