squid: upgrade to 3.5.7

1. Remove the squid-change-ksh-referen*.patch which is not needed, since
   3.5.7 did not use ksh by default.
2. Update the checksum of COPYING,since the date in it has been changed.
3. Define BUILDCXXFLAGS, otherwise the target gcc options -std=c++11 will
   add into it, and lead to building failure since host gcc maybe not
   support "-std=c++11"
4. Assume to support GNU atomic operations by default, the running check
   on cross-compile setup does not work
5. enable basic auth by checking the DISTRO_FEATURE, and the default
   dependency on db, opensasl and openldap nis have been set, so enable
   them by default.

Signed-off-by: Roy Li <rongqing.li@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Joe MacDonald <joe_macdonald@mentor.com>