[staleness] special-case realloc to ignore libc copy?

_From [derek.br...@gmail.com](https://code.google.com/u/117968039472581148324/) on December 10, 2010 19:52:18_

PR 553728

if app calls realloc() should the shifted memory retain its old staleness
values or should it now all be "recently touched"? if app has data struct
w/ some fields that are never touched but it resizes something else that's
part of data struct it seems better to report the untouched fields as
stale. right now the realloc libc code will touch it all.

_Original issue: http://code.google.com/p/drmemory/issues/detail?id=225_