Fix the list of static functions coming from swab.h to match the
ones exported by glibc.
Force the definition of __HAVE_BUILTIN_BSWAP{16,32,64}__ so the headers
use the builtin.
Add a unit test to guarantee that kernel header updates do not break this.
Test: Built and booted angler.
Test: Built the bionic unit tests for arm, arm64, mips, x86, x86_64.
Test: Ran the new test on angler and glibc.
Change-Id: I4ce229e3f198c204186d72bf22dd97b5cdf239e4
ee1e0a34ae