- Link with -pthread instead of -lphtread.
- Use VERSION (consistent with other ports, although it's still not a
rule) and propagate it where needed.
- Propagate SO_VERSION using MAKE_FLAGS.
- Fix MASTER_SITES.
- Remove a bunch of patches that prevented .so links to be created, use
a post-install target to remove them instead.
Discussed with and ok ajacoutot@
