strace: Version bump to 4.7

This also fixes a compilation problem with kernel headers 3.5
http://autobuild.buildroot.net/results/bb66a3a06d26f558e1c4c0593bb68e7af1d82398/build-end.log



Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>