eliminate duplicate copies of DR libs in release package

_From [bruen...@google.com](https://code.google.com/u/109494838902877177630/) on May 10, 2012 13:29:00_

frontend now imports from DR and thus needs a copy of dynamorio.dll, as of r823 which creates the pcache dir in the frontend:

```
dynamorio.dll
59 dr_directory_exists
55 dr_create_dir
```

while we could move that into drmemorylib, I deliberately used the DR API, and we may want to replace other windows-specific API's in the frontend, to make it cross-platform and re-use it on linux where eventually we may have a libdrinject.so. so we don't want to get rid of the imports. but, now we need to copy dynamorio.dll into bin/. this makes multiple copies in the drmemory release package. drinjectlib and drconfiglib are also duplicated. this issue covers trying to reduce those copies.

_Original issue: http://code.google.com/p/drmemory/issues/detail?id=885_