add LDAPLibraryDebug directive to mod_ldap to turn on

tracing in underlying LDAP SDK, where all the interesting tidbits
about all kinds of LDAP errors are hidden.

Unfortunately windows doesn't implement this LDAP_OPT.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@831183 13f79535-47bb-0310-9956-ffa450edef68