squid: drop session external acl helper, use file_userip

The session external acl helper needs berkeleydb, switch to the basic
file_userip one which was my original intention (renamed from ip_user in
the 3.3.x series). Fixes:
http://autobuild.buildroot.net/results/635/6359137cde3b293d46df732836b8966d30f23cbc/

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/squid/squid.mk

@@ -25,7 +25,7 @@ SQUID_CONF_OPT =	--enable-async-io=8 --enable-linux-netfilter \
 			--enable-auth-negotiate="wrapper" \
 			--enable-auth-ntlm="fake" \
 			--disable-strict-error-checking \
-			--enable-external-acl-helpers="session"
+			--enable-external-acl-helpers="file_userip"
 
 # On uClibc librt needs libpthread
 ifeq ($(BR2_TOOLCHAIN_HAS_THREADS)$(BR2_TOOLCHAIN_USES_UCLIBC),yy)