separate debug info into separate files from the main release packages

The 7.0 release is significantly larger than 6.2, due to the static DR library:

25MB larger:
111132 DynamoRIO-Windows-6.2.0-2.zip
136356 DynamoRIO-Windows-7.0.0-RC1.zip

Unpacked it's 92M larger:
```
# du -sh DynamoRIO-Windows-7.0.0-RC1 rel-6.2.0/DynamoRIO-Windows-6.2.0-2
536M DynamoRIO-Windows-7.0.0-RC1
444M rel-6.2.0/DynamoRIO-Windows-6.2.0-2
```

37M of that is adding drcachesim (pdb's are large!)
The rest is the static DR build, which is huge: 15MB each x 4!

Linux is also much bigger:

98312 DynamoRIO-Linux-7.0.0-RC1.tar.gz
75036 DynamoRIO-Linux-6.2.0-2.tar.gz

Also from static DR: 20MB each x 4!

Should we consider putting the pdb's and .debugs in a separate package?
That cuts Windows more than in half: shrinks from 536M to 242M.
For Linux, from 319M to 231M.