ldb: Release ldb 2.0.4

ldb: Release ldb 2.0.4

* copy the ldb_options passed to ldb_connect onto the ldb_context,
  making them more generally available.

* fix index buffering.
  As a performance enhancement the indexes are cached in memory during a
  transaction, and written to disk as part of the prepare commit. The
  indexes could become corrupt in the event of a failed operation.

* fix read beyond buffer
  Calling the "ldb_parse_tree" function with a filter consisting of
  exactly a single space (" ") would trigger a read beyond the input
  buffer.
  BUG: https://bugzilla.samba.org/show_bug.cgi?id=13900

Signed-off-by: Gary Lockyer <gary@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>