support passing absolute addresses to symquery

_From [bruen...@google.com](https://code.google.com/u/109494838902877177630/) on December 06, 2013 16:23:22_

In many cases the addresses we want to look up are absolute. If the module
has been rebased, it makes sense to force the user to figure out the
offset. But for an (non-PIE) executable, when used in an addr2line-like fashion, it
would be nice if symquery could figure out the preferred base on its own.

Currently there's no DR interface to get the preferred base.

_Original issue: http://code.google.com/p/drmemory/issues/detail?id=1398_