slapd update: LDAPv3 schema work

["Kurt D. Zeilenga" <Kurt@OpenLDAP.org>]

The new schema code is slowily taking shape.  Most of the
framework is in place and I'm working on getting basic
operations to use the new code.  At present, Root DSE
and cn=schema searching works with present and equality
filters (where syntax and matching rules are implemented).
Others are welcomed to help flush out missing syntax and
matching rule handlers and/or extend the filterring code
to handle other choices.

No backend, other than back-dnssrv, is currently working.
I'll likely get back-password working before attempting
back-ldbm (as the index code rework will be messy).  Others
could likely get other non-indexing working fairly easily.

All this, of course, is behind -DSLAPD_SCHEMA_NOT_COMPAT.
Free free to toy with it... it WILL crash... patches
welcomed.

Yes, before the next alpha, we will run
	unifdef -DSLAPD_SCHEMA_NOT_COMPAT ...

but it has to work first.

	Kurt