Bug #935: squid_ldap_auth can be confused by the use of reserved characters

Bug #935: squid_ldap_auth can be confused by the use of reserved characters

squid_ldap_auth may be confused by the use of reserved characters allowing
the login name to be masqueraded in different manners possibly allowing the
user to partially bypass certain per-user restrictions or confuse third
party accounting packages.

Note that the user can not bypass the login procedure as such. All he can
do is to make the login name look different than normal. There is still
full audit trails on who the user is etc.

The patch also adds and documents a -d flag to both squid_ldap_auth and
squid_ldap_group to allow for easier tracing of the operation of these
programs if results is not what is expected.