More backglue fix: do not return NO_SUCH_OBJECT when the base object is located above the subordinate database in search

1) Return NO_SUCH_OBJECT if base object cannot be located
2) Does not search databases that are superior to the base object of the search

Make sure sizelimit errors are propagated.

glueBack->be_entry_close before calling it

fall into the regular send_ldap_* functionality instead of calling into
those functions explicitly. Nested callbacks still aren't handled as
cleanly as they might be.

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.

backends to be called directly, instead of having to wrap every function.
Delete unneeded wrappers.