Monkey with JarUrlConnection to make it work when LANG unset

The problem all along has been in AsciiBytes, so the fix in
commit ce3aaf was just a stop gap for a system where multi-byte
characters are supported but the default encoding is not UTF-8 (e.g.
most Windows systems). The real solution is not to leave it to
chance and always pick an encoding for the JarEntry names (i.e.
in AsciiBytes).

Fixes gh-764