If configure is generated with xorg-macros 1.16 or later, this allows
builders to --enable-unit-test and run the tests other than the xi2
tests which require ld -wrap (and are still wrapped in if HAVE_LD_WRAP
in tests/xi2/Makefile).  If an older xorg-macros is used, the existing
behaviour is preserved of requiring ld -wrap for all unit tests, but
no side effects occur, so the minimum xorg-macros version is not raised.

If unit testing is enabled without ld -wrap, then we create a bogus
"xi2-tests" script just to report that we're skipping them.

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Jeremy Huddleston <jeremyhu@apple.com>