squid3 LDAP config.test

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

www/squid3's LDAP helpers don't build on a system with non-native LDAP.

The problem is that the config.test scripts in basic_auth/LDAP,
digest_auth/LDAP and external-acl/LDAP-group explicitly test for the presence
of /usr/include/ldap.h.
Is the fix just to patch an "exit 0" into those scripts (which works)?
Or is the correct method to generate config.test scripts based on the
(potentially several) members of BUILDLINK_INCDIRS.openldap-client=

There's also a splling error in options.mk: fileuser_ip -> file_userip.