Updated tolerances because the command line argument, -p, is now used in test27cells.c to perturb the smoothing length and not just the default value of 1.1f.

Updated the way we converge towards the smoothing length. We now use a Newton-Raphson scheme. This applies to the Gadget-2 scheme.

Do not call the difffloat.py script with the additional deprecated parameters formerly used for rho_dh

Move rho_dh into the density sub-structure. Update the pressure and sound-speed after kick and drift

Updated 'make check' scripts with newer tolerances for the Intel compiler and made the scripts choke if files are missing