Multiple entries in proxy.auth do not work as specified in documentation

[Kamilcuk]

The following:

proxy.auth = name=default;type=basic;file=/passwd/default.htpasswd                                                                               
                     name=kamil;type=basic;file=/passwd/kamil.htpasswd    

Does not work and second entry is ignored.

The following does work:

proxy.auth = name=default;type=basic;file=/passwd/default.htpasswd,name=kamil;type=basic;file=/passwd/kamil.htpasswd    

It is parsed with https://github.com/fabiolb/fabio/blob/642e425cf664e23d257ca357b7b1bfd1e432683d/config/kvslice.go#L20