Traffic Flow equation with an on ramp source

Traffic flow equations with a delta function source term representing an on ramp at x = 0. This is implemented using the fractional step approach in src1.f.

Example [book/chap17/onramp] to accompany the book Finite Volume Methods for Hyperbolic Problems by R. J. LeVeque.

Converted to Clawpack 5.0 form in 2013.