John Lightsey filed bug report #1999181: "CLOCK_MONOTONIC always fails on

some systems" (http://curl.haxx.se/bug/view.cgi?id=1999181). The problem was
that the configure script did not use the _POSIX_MONOTONIC_CLOCK feature test
macro when checking monotonic clock availability. This is now fixed and the
monotonic clock will not be used unless the feature test macro is defined
with a value greater than zero indicating always supported.