failure in slap_op_free is possible)

the conn->c_pending_ops queue.

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.

for the known exops.

using LDAP_DEVEL (to indicate experimental) to enable experimental features
(true for HEAD unless LDAP_REL_ENG is defined)