Also, fix slapi_dn_parent() crasher

we support Slapi_DN API)

entry_schema_check() nows takes Operation instead of Backend as first
argument, allows it to check o_no_schema_check

global SLAPI plugins) have access to op->ora_e.

Note that slap_mods2entry() is still called in fe_op_add() in order to
add any operational attributes.

for overlay ops

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.

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

Support for SLAPI internal operation plugins.

renamed slapi_int_init_connection => slapi_int_connection_init for consistency; blind fix to ITS#3879

Allow internal operation pblock to forward connection/operation parameters

as the canonical argument (wrappers for old APIs are provided)

  patch provided by Martin Evans