This patch removes the conditional compilation of ATCDCL, compiling both
the old and new ATC systems. The old system only provides ATIS, AWOS and
some dialog lookups, and hence should not conflict with the new system.
HAVE_CULLSETTINGS_CLEAR_MASK was not set, so a program to test
CLEAR_MASK was added. The Posix timer function clock_gettime is in
librt on Fedora, and probably on other systems too.