This is an exact Riemann solver for a general equation of state.  It
follows the outline for Colella & Glaz 1985, section 1.  This is too
slow to use in an actual hydro run, but instead is intended to
generate exact solutions to the Riemann problem for comparison with
Castro shocktube output.  Several inputs files for Helmholtz EOS-based
shocktubes are provided.

This solver is used in Zingale & Katz (2014), and more details are
given there.

To build the solver, simply type 'make' in this directory.


Note: at the moment, we compile in a network from Microphysics, but
we don't use an integrator.  This is not needed since the GPackage.mak
in the network has the network dependent code blocked out with an
`ifneq ($(USE_REACT), FALSE)`
