corrected the isAccepted table accorrding to RFC 1630

The '/' character is stop to escape due to this commit ca80cbb.
This cause some browser cannot redirect to the original requested page.

Actually, this table isn't correct for lot of characters, so I also
correct it.

'&' is a valid character of xalphas.
However, we still need to escape it, otherwise we can't distinguish it
is a part of the `redir` or a separator.
add the missing querystring of the URL

For the current version, the query string is missing in splash page.
This bug was induced by the commit ca80cbb, which contains only some
part of patch form wifidog: http://dev.wifidog.org/changeset/1239 .
changed -lpthread to -pthread of LDFLAGS

For the newer version of GCC, the placement of -l option does matter,
and it cannot compile successfully now. Libraries must be specified
after the objects in the linking command.

Also, there is another option -pthread which seems more preferred.