example/mesh: add missing header files
Make a demo that crashes join_faces
Possible partial fix
Second partial fix
Extend example/mesh/periodicity
Write p8est_connectivity_face_neighbor_corner
Tweaks
Add defines to facilitate Fortran 90 wrapping
p6est: fix unused
Remove warning
Update error message
Revert "example/mesh: add missing header files"

This reverts commit f063a3b7db0ee20fcce0c7bee761e4c143fccde6.
Merge warning fixes into develop