support for multi-values attribute in Component Matching

See "contrib/slapd-modules/comp_match/README" to understand
what's the purpose of  this patch is and how to use it.

filterentry cleanup

(needs to be applied to other filter cases)

	(entryDN:isSubordinate:=dc=example,dc=net)
isSubordinate should be implemented in component matching terms

extensible matching (the main objective) coming soon.
(This stuff should really be table driven (for extensibility reasons).)

Need to implement filter support (for entryDN and subschemaSubentry).
Fixed hasSubordinate assert() bug in entry filters

and "implementing GSER and Component Matching" in ODD 2004.
All codes are #ifdef'd with LDAP_COMP_MATCH.
test031-component-filter works correctly only when the LDAP_COMP_MATCH macro is set.
To disable it, set AC_WITH_COMP_MATCH "no" in "openldap_src/tests/run.in".

Add better approx test

consolidated into the Operation structure. All reply parameters
are consolidated into the new SlapReply structure. Most operations
now have identical call signatures... Changes are not #ifdef'd,
revert to -r NO_SLAP_OP_BLOCKS if necessary to back out.

no normalizer, a_nvals = a_vals.

	schema engine updated (but not schema routines so things don't run yet)
	nvalues mostly populated, enough for tests 0-2 to pass
	schema routines needs lots of work
	modify/mods codes needs lots of work