Use the SC_VERSION autoconf macro

Conflicts:
	sc
Revert to ax_prefix_config.m4
Remove restrict keywords
Merge old maintained 'v0.3.4.2' into mainline
Add option to recreate old timings checksums
Make timings partition-independent
Add latest checksums to timings
Fix bug in p4est_nodes with node-empty processors
Update libsc
Merge branch 'next' into develop