package/pax-utils: needs kernel headers >= 3.5

pax-utils require a toolchain with kernel headers >= 3.5 to provide
PR_SET_NO_NEW_PRIVS.

Fixes:
http://autobuild.buildroot.net/results/a9e/a9e0287e67c03e5e385bf54578aa6c5c85206ec2



Signed-off-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>