without string[len] == '\0' causes assert in ldap_dn2bv_x.

fix several minor issues with using dangling pointers and uninitialized data
fix caching of privileged connections
fix issues with unresponsive target failures during search

Preserve delete/replace indication from original request

fix concurrency issue when binding before a search; rework and cleanup data structures (remove unused members)

a server is unwilling to make use of a known critical control.

Remove unnecessary ISOC notices