Fix typos and tweak documentation
Merge remote-tracking branch 'upstream/develop' into develop

Conflicts:
	src/p4est_mesh.h
Tweak documentation
Fix MPI warning in lnodes
Replace some P4EST_MPI with P4EST_ENABLE_MPI
Run s/P4EST_DEBUG/P4EST_ENABLE_DEBUG/
Some search and replace in test
Some search and replace in examples
mark error on website
Update libsc for config fixes
Tweak web page
Merge minor web page update
address some compiler warnings
P4EST_MPI->P4EST_ENABLE_MPI in ghost
Write face_neighbor_corner_orientation
Simplify one neighbor_corner_set situation
Fix some warnings with --pedantic
Merge neighbor_corner functions
Fix another warning
Update libsc