plt/racket — pull request #767 by m4burns (2014-08-31 22:44:11+00:00)
Title: unzip: Handle non-seekable input ports.

Before this commit:
- unzip would attempt to seek the input port via file-position in some cases

After this commit:
- unzip attempts to seek the input port via file-position. If
exn:fail:filesystem or exn:fail:contract is thrown, unzip skips over bytes
from the input stream to achieve the desired seek.