Fix bug in core::string stream unpacking
Fix bug in core::string stream unpacking

operator<< has to be in the right namespace to work (but why?)

serge-sans-paille/pythran,serge-sans-paille/pythran,pombredanne/pythran,hainm/pythran,pombredanne/pythran,pbrunet/pythran,hainm/pythran,pbrunet/pythran,hainm/pythran,pombredanne/pythran,pbrunet/pythran,artas360/pythran,artas360/pythran,artas360/pythran