oLschema2ldif: Resolve multiple parsing bugs

oLschema2ldif: Resolve multiple parsing bugs

The "oLschema2ldif" program contained multiple bugs triggered by
malformed inputs:

* Iteration beyond list of recognized dsdb syntax OIDs when value wasn't
  found (bug 9567)
* NULL pointer dereference when input didn't define a name
* Heap buffer overflows for unterminated token values

Tests are added to reproduce all identified bugs.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=9567

Signed-off-by: Michael Hanselmann <public@hansmi.ch>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Then adapted to use ARRAY_SIZE() consistently as suggested by
metze.

Autobuild-User(master): Andrew Bartlett <abartlet@samba.org>
Autobuild-Date(master): Wed Apr  3 02:43:07 UTC 2019 on sn-devel-144