I note that these environment variables are specific to Linux, and then only certain Linux systems. If we add these, then we should also add similar environment variables for FreeBSD malloc(3), MacOS/X malloc(3), and various alternative malloc(3) libraries. And then we might get into cases where variables for one set of environmental variables conflict with another. As these can be set by the developer as desired in their development environment, there's little reason to get into setting all the malloc(3) environmental variables that might be useful... and we shouldn't play favors and only set variables for Linux.
-- Kurt