Another round of those unportable config/build changes :-/

* Add option to build with OpenSSL out of the box. Fix thusly exposed
  bit rot. Although it compiles now, getting this to do something
  useful is left as an exercise.

* Fix Kerberos options to defer checking for required libraries until
  all the other libraries are checked for.

* Change default odbcinst.ini and krb5.srvtab path to PREFIX/etc.

* Install work around for Autoconf's install-sh relative path anomaly.
  Get rid of old INSTL_*_OPTS variables, now that we don't need them
  anymore.

* Use `gunzip -c' instead of g?zcat. Reportedly broke on AIX.

* Look for only one of readline.h or readline/readline.h, not both.

* Make check for PS_STRINGS cacheable. Don't test for the header files
  separately.

* Disable fcntl(F_SETLK) test on Linux.

* Substitute the standard GCC warnings set into CFLAGS in configure,
  don't add it on in Makefile.global.

* Sweep through contrib tree to teach makefiles standard semantics.

... and in completely unrelated news:

* Make postmaster.opts arbitrary options-aware. I still think we need to
  save the environment as well.