package/dawgdic: needs gcc >= 4.7

std::strtoll is only supported since C++11.

Fixes:
http://autobuild.buildroot.net/results/cae/cae3cda9be779ea8359f94d13bbbca97e68495ca/



Signed-off-by: Romain Naour <romain.naour@openwide.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>