Add more infrastructure to be used for fixing #275284 (Valgrind

Add more infrastructure to be used for fixing #275284 (Valgrind
memcpy/memmove redirection stopped working in glibc 2.14/x86_64), but
don't fix the problem yet.  Should be no end-user visible change.

* in m_redir.c, when processing redirection specifications, consider
  all the names associated with an address, not just the primary name.

* add plumbing to support the notion of "behavioural equivalence class
  tags" of redirect/wrap functions.  These can be used by m_redir to
  resolve some situations in which the available set of redirect
  specifications causes some address to get redirected to two
  different functions.  (Framework is in place, but such resolution is
  not implemented yet.)

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@11984