provide more info on indirect leak group members

_From [bruen...@google.com](https://code.google.com/u/109494838902877177630/) on August 23, 2011 21:00:47_

when up-pointers are used, the child can end up being the anchor reported
for an indirect leak group, which can be misleading. if the parent is
usually larger, the largest object in the group could be reported. or,
under some kind of leak verbosity option, all members of the group could be
reported.

xref example at https://code.google.com/p/valgrind-variant/wiki/LeakCheckingProblems

_Original issue: http://code.google.com/p/drmemory/issues/detail?id=565_