features/glupy: Add mem accounting support

When glusterfs is built from source using -DDEBUG flag and glupy
xlator is added to vol file, the brick process used to crash when
mounting the volume.

This fix is largely derived from the fix submitted for BZ #1035751.
Thanks to Justin Clift for helping in tracking this down.

BUG: 1035751
Change-Id: Id64f92eecc9335e34dd08812fe176774e7723c2c
Signed-off-by: Prashanth Pai <ppai@redhat.com>
Reviewed-on: http://review.gluster.org/7332
Reviewed-by: Jeff Darcy <jdarcy@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>