RFR: 8029607 Type of Service (TOS) cannot be set in IPv6 header

[Michael McMahon]

Could I get the following change reviewed please?

http://cr.openjdk.java.net/~michaelm/8029607/webrev.1/

It adds support for the IP_TOS socket option to ServerSocketChannel
(and ServerSocket). This means
that the type of service/traffic class can be set on a server socket
and therefore the option set on the responding SYN packet
for incoming connections.

It also fixes a problem where both IPv4 (TOS) and IPv6 (traffic class)
couldn't be used in the same VM instance. After the fix, it still only works
properly in Linux. Windows has an entirely different (non API based)
mechanism for this. Other OS'es may provide the underlying support in
future.

Thanks,
Michael.