Use the SC_VERSION autoconf macro

Conflicts:
	sc
Revert to ax_prefix_config.m4
Remove restrict keywords
Edits on comments in p4est_lnodes.h
Move extern C into proper place
test of degenerate case of lnodes
started work on extending iterate

- execute at indirectly touched entities
- provide more information at corners/edges
  this should allow lnodes to simplify a lot once it's done
Added p4est_iterate_ext
some documentation for the new faces/edges fields of side info in p4est_iterate.
Merge branch 'test-lnodes' into iterate-ext
cleaned up the control-flow in iterate
iterate: fix bug in determining cside faces
iterate: sort intertree inputs, so lowest is always first
lnodes simplification
small fixes in lnodes
iterate: fix edges bug
Merge branch 'fix-iterate' into simplify-lnodes
iterate: small bug fix in init_edge
iterate: fix bugs for remote callbacks
lnodes: fix bugs from simplification, tests cleanly