New port: devel/memleax

Memleax debugs memory leaks of running processes by attaching to them,
without recompiling or restarting. It hooks the target process's invocation
of memory allocation and free and reports the memory blocks which live
long enough as memory leak, in real time.

It is convenient to use, and suitable for production environments.
There is no need to recompile the program or restart the target process.
You can run memleax to monitor the target process, wait for the real-time
memory leak report, and then kill it with ctrl-c to stop monitoring.

WWW: https://github.com/WuBingzheng/memleax

PR: 217105
Submitted by: Guy Tabrar <guy.tabrar@me.com>
Approved by: lme (mentor)
Differential Revision: https://reviews.freebsd.org/D9725