Bug 12 [configure.ac] add sys/bitypes.h to int64_t tests

Bug 12 [configure.ac] add sys/bitypes.h to int64_t tests
based on patch by mooney@dogbert.cc.ndsu.nodak.edu (Tim Mooney)
Bug 45 [configure.ac] modify skey test to work around conflict with autoconf
reported by nolan@naic.edu (Michael Nolan)
patch by  Pekka Savola <pekkas@netcore.fi>
Bug 74 [configure.ac defines.h] add sig_atomic_t test
reported by dwd@bell-labs.com (Dave Dykstra)
Bug 102 [defines.h] UNICOS fixes. patch by wendyp@cray.com
[configure.ac Makefile.in] link libwrap only with sshd
based on patch by Maciej W. Rozycki <macro@ds2.pg.gda.pl>
Bug 123 link libpam only with sshd
reported by peak@argo.troja.mff.cuni.cz (Pavel Kankovsky)
[configure.ac defines.h] modify previous SCO3 fix to not break Solaris 7
[acconfig.h] remove unused HAVE_REGCOMP