fixes issue 521 + start over at TOS when building callstack   w/ legitimate-looking ebp that points at   invalid values
fixes issue 521
+ start over at TOS when building callstack
  w/ legitimate-looking ebp that points at
  invalid values

git-svn-id: fe3cd4388a6e5a968b09397a3d721fe124e8117a@428 5b54908e-ead4-fc18-b48a-0285e6dbc711

rnk/drmemory,rnk/drmemory,rnk/drmemory,rnk/drmemory