fix translucent overlay test when back-monitor is compiled as module (privately reported by Buchan Milne)

an integer or long integer parameter, the value argument is a pointer to
the integeral value rather than the value itself.

structures

This removes a lot of copying. It's still a bit tricky where the internal
slapd data types are different to those exposed via SLAPI (eg. modifications)
or the internal values are not allocated on the heap (eg. controls). Some
copying is necessary in these cases.

add back-config suppor to back-monitor; advertize what backends provide back-config support; HEADS-UP: changed monitor OIDs (reflected in OID repository)

duplicating frontend code, and o->o_callback rather than overriding
entry send clalbacks.

Support for SLAPI internal operation plugins.

add infrastructure to register verbmasks; allow to register loglevels programmatically; cleanup glue protos