improve suppressions to avoid default suppressions w/ mod+offs

_From [bruen...@google.com](https://code.google.com/u/109494838902877177630/) on January 10, 2012 15:09:46_

from older notes:

mod+offs is really for end users and not as easy to use in default supp b/c we
need to cover all versions of the dll -- though w/ a leak something like issue #498
can't be used so w/o some auto-symbol-acquisition solution which has its own
problems there's no simple solution.

in issue #446 text:
xref issue #475 and issue #504 where for the first time a default suppression has to
use mod+offs (for rsaenh.dll)

issue #498 actually enabled me to remove the issue #504 mod+offs suppression

for leaks, to avoid mod+offs and yet not be too general:
- could allow specifying the size of the leak
- specify offset from start for possible leak
- xref issue #738 for any # frames in one module

_Original issue: http://code.google.com/p/drmemory/issues/detail?id=741_