Added dbg_error_log() calls for error msgs

If the ldap driver is not valid, the error messages were not printed.
There was just "Couldn't contact LDAP server for authentication" - But
why?

This commit adds a print loop for all messages from the global
$c->messages message array.
Merge pull request #13 from matthiasbeyer/ldap_error_output

Added dbg_error_log() calls for error msgs