Patch error in the usage fonction : calling Mmg with -h or -val option was leading to call argc times the function.

Add a very rough evaluation of the edge length histo (no particular treatment of the interface edges.

Remove unused function : PMMG_oldGrps_cleanMesh (linked lists for tetra/points, etc. + reallocation).

Remove unused function : PMMG_pack_grps_norealloc (remove the groups without mesh from the group array and pack the group array.

Fix asymmetrical weights on grp graph edges referencing OLDPARBDY faces.

See merge request ParMmg/ParMmg!23

Bugfix/sanitizer linux

See merge request ParMmg/ParMmg!24

Feature/weights

See merge request ParMmg/ParMmg!22

Fix for multidomain cases.

This reverts commit ccd0d949.

Revert "Move deallocation of int_face_comm->intvalues from merge_grps to split_grps, in order to keep track of old parallel faces."

This reverts commit 24e8eb64.

Do not impose contiguity if using Parmetis, or if a discontiguous group is found.