add/merge as we now free strings agressively.  Improved debug
message to include name of missing required attribute and added
check for 'operational attributes'.  This check should be used
everywhere we need to test for operational attributes (add/modify).
Also, enabled schema checking for tests (and fixed resulting
problems by adjusting oc.conf).

  "Check that the entry has no writers before removing it from the
  cache" sounds more sensible to me than "check that it *has* writers"
  before removing it.
I've also changed the default cachesize for tests to 4.  This
should help discover such problems.

Update Install document with testing step and other minor changes.

Now to sort out configure enable/with options.

Added NO_THREAD support to configure.in.  (Still need thread lib detection)

	SHA1 support is contributed by Daniel J. Gregor <dj@gregor.com>
	MD5 support is contributed by me <kurt@OpenLDAP.org>
	Uses public domain MD5 routines
	Uses ISC/IBM freely redistributable Base64 routines
	SHA1 support requires external SHA1 routines

Patch provided by dj@gregor.com.

Patch provided by dj@gregor.com.

	adds POSIX RegEx (and removes BSD re_comp/re_exec) support.
* POSIX RegEx is not currently included in the distribution, however
	we will probably add Henry Spencer's REGEX library soon.
* ACL Group functionality is also included in this merge!