Add min_images_only argument to update_hysteretic_region()

If present and true, we only need to compare first column of inner
and outer tables.

Fixes possible bugs when bond-hopping leads to inequivalent shifts for the
same physical atom.
Bug fix to segmentation fault in find_lattice_correspondence()

When max_n_neighbours > l_n_neighbours count(match_list /= 0) is not reliable:
now replaced by count(match_list(1:l_n_neighbours) /= 0).
Fix bug in handling of has_fixed in Potential_Precon_Minim preconditioner builder

Conflicts:
	libAtoms/minimization.f95
Respect qm_force_periodic setting regardless of qm_little_clusters
Added cluster_hopping_skip_unreachable option to remove buffer atoms no longer reachable by bond hopping
Add timing around LOTF fit call
removed reference to gc121mac1 in  Makefile.config
Make hook be passed into precon_minim explicitly, to allow for more arbitrary hooks.  Potential.f95 still exports print_hook, which is passed in by eval.f95.  Should do this for other potential minim routines as well
definitely fixed oboes this time, plus change so initial alpha is estimated differently for unpreconditioned LBFGS
forgot to uncomment a couple lines before committing
Added warning about buffer_hops=0, transition_hops=0 edge case to create_hybrid_weights()
tweaks to precon_minim to improve the performance of unpreconditioned CG (and maybe others)
rework of last commit to not interfere with existing preconditioned performance
fixed matrix multiplication in phonon path calculation
Bug fix to ringstat: do not assume short-circuit boolean evaluation with present()
More info about terminating H positions at ANAL verbosity
first (not quite working) draft of precon_dimer
norm2 -> normsq to use function in libAtoms linearalgebra module (needed for compilers that lack norm2() intrinsic, introduced in Fortran 2008
normsq() -> norm() for consistency of output
Allow fit_method to be either lotf_adj_pot_minim or lotf_adj_pot_svd when extrapolate_steps != 1