Looks like the implementation was derived from Mozilla's
nsProxyAutoConfig.js, which is evaluated twice. It requires double
escaping.
In our case excessive escaping is harmful.
In particular it makes ip-matching regexp in isInNet() invalid and makes
it really slow as we go to dnsResolve() all the time, even when it's not
needed.
Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>