MFH: r361462

- Fix build with clang (overzealous -Werror)
- Add staging support
- Respect CFLAGS, LDFLAGS
- Convert to new LIB_DEPENDS format
- Fix WWW line in pkg-descr

Approved by:	portmgr (erwin)
Make sysutils/pstree operable in jailed environment.

(cherry picked from commit 0aa00da618ffa2bc5b4c4f8b89be22b9df2e9936)
Fixed replacement of $(PGBOUNCER_RUNDIR) in files/pgbouncer.in