Fix fish build
Fix a memory error in fish.advance: out-of-bounds index on array start
Start work on self-gravity module
Add local Poisson solver to 1d self-gravity problem
Use more appropriate function and file names for 1d self-gravity problem
Set up a sound wave problem to move toward testing grav1d

Also, in this commit the grav1d module is given quite a bit more
control from Lua, rather than being just a single function.
Fix a bug in the parsing scripts, setting double to int
Start generalizing grav1d
Allow arbitrary resolution on grav1d module
Add exact solution (without gravity) to gravity wave problem
Include Jeans length in grav1d setup, not in dispersion relation yet
Fix a bug in the mapbuffer function, must get nq = fluids_descr_getncomp
Introduce RK3 in grav1d, studying density wave and pure sound wave
Demonstrate working sound wave with gravity-modified dispersion

Convergence rates non-gravity density wave problem are demonstrated to
be 2 with PLM+HLLC, and 4 with spectral WENO5. Comparison with Mara
should be done next.

Gradually moving control of grav1d back to Lua. Now the solver gets
configured by Lua code, next have the fluid descriptor as well.
Fix bug in parse_fish.py, give control of fluid descriptor to Lua
Add outflow boundary conditions to grav1d

For uniformity, we also move the time update flag to fish.h, along with
the boundary conditions flag.

There is a mysterious behavior where sometimes PLM reconstruction looks
like it's doing PCM. Putting printf's in the _plm function shows that
it's indeed being called. For some reason, rebuilding reconstruct.c
appears to fix the problem when it happens. Valgrind does not report
anything suspiscious.
Respect USE_FFTW in fish build
Clear the INCLUDE macro before using it
Continue improving robustness of Linux / icc build
Fix newly introduces broken builds on darwin