Use SIG_DFL instead of 0
Use SIG_DFL instead of 0

Those are the same on my system, except that the former is defined by
POSIX and the latter is undefined behavior.

Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh