Synopsis
		sfshotconstkirch < inp.rsf > out.rsf aal=y nx=ns dx=ds x0=s0 offset=n vel=

Requires the input to be in (time,offset,shot)

Parameters
		bool aal=y [y/n] if y, apply antialiasing   float dx=ds   int nx=ns   bool offset=n [y/n] if y, the output is in offset   float vel= velocity   float x0=s0