r7527: - added a ldb_search_bytree() interface, which takes a ldb_parse_tree

r7527: - added a ldb_search_bytree() interface, which takes a ldb_parse_tree
  instead of a search expression. This allows our ldap server to pass
  its ASN.1 parsed search expressions straight to ldb, instead of going
  via strings.

- updated all the ldb modules code to handle the new interface

- got rid of the separate ldb_parse.h now that the ldb_parse
  structures are exposed externally

- moved to C99 structure initialisation in ldb

- switched ldap server to using ldb_search_bytree()
(This used to be commit 96620ab2ee5d440bbbc51c1bc0cad9977770f897)