Simon McVittie authored May 04, 2015 and Colin Walters committed Nov 22, 2016

This code assumes that int is exactly 32 bits, and that pointers
are either 4 or 8 bits, on platforms with __ATOMIC_SEQ_CST.
In practice this is going to be true.

A previous attempt at this assertion placed the G_STATIC_ASSERT
at the top level in gatomic.h, but that broke anjuta, which
redefined __unused__ at the time. These assertions are about the
platform/compiler ABI, so it's sufficient to check them once,
while compiling GLib itself; accordingly, move them to the
implementation.

Bug: https://bugzilla.gnome.org/show_bug.cgi?id=730932