Compile the gravity code as a separate convenience library. Use special compilation flags for this library. When compiling on AVX512, add extra flags to compile the gravity files.

Need to make sure that AX_CC_MAXOPT doesn't assume we have set CFLAGS and it should not extend them (ac_test_CFLAGS=yes)

Merged in new upstream version of the maxopt autotools macros that fixes the problem or erasing the CFLAGS.

Added a new particle type for DM boundary particle in zooms. Created a new flavour of gravity: multiple-sotening.

Prevent users from compiling the EAGLE BH model without the gravity scheme that computes potentials.

Increased the version number following the addition of the on-the-fly FOF code and black holes seeding.

Increased version number following the addition of star-formation and feedback jointly over MPI, black hole accretion and feedback (also over MPI), refactoring of the hydro parameters, improvement to the memory footprint and completion of first fully-fledged EAGLE runs.

Correct the external potential help string to not include the now-defunct softened isothermal potential.

Added basic support for black hole particles. Particles can be read in, attached to gpart, integrated forward in time, drifted and written to snapshots.