Misc Clean.

returned for Bind operations, instead invalidCreditials
should be returned.

This had the effect of setting the result code to LDAP_SUCCESS for modlist == NULL
even on a replica when an update-ref might be set. This was causing a plugin (that
implements the commit phase in a post-op plugin) to write to "read-only" replica.

macro).  Add comment indicating configure test needed.

list and a subsequent plugin aborted the operation -- regardless of the
preop result the frontend must refetch the array of LDAPMods

added new test slapd-modify (based on slapd-modrdn). Adds a single attribute to an entry and removes it again.

- Remove unused variables
- Remove the attribute for component filter test in core.schema

opinfo isn't

headers in two places? :))

returned by the plugin, rather than that requested by backend_attribute(),
for ACL checking.

They should of course be the same but this is the "correct" approach from
both a security and readability perspective

real value

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".

This allows computed attribute plugins to also provide their attributes to
the ACL engine, for example