devel/valgrind-devel: update to Paul Floyd's FreeBSD valgrind branch
This branch rebases us forward to Valgrind 3.17.0, incredibly current as
of today. It also fixes a vast array of known issues, making valgrind-devel
actually functional on 13.0-CURRENT and fixing most of the regression tests
All patches previously in the port have been incorporated.
There are still some open issues remaining:
This port is believed to be largely functional enough to get wider testing. Many,
many thanks to the excellent work of Paul Floyd to modernize our valgrind port.
Paul's informed me that some of these issues will still get closed today, so I'd likely hold off on committing it for just a little bit.