8217451: ExtendedSocketOptions should encapsulate support for SO_FLOW_SLA

[Alan Bateman]

ExtendSocketOptions is the supporting class that the socket 
implementations use for JDK-specific socket options. Vyom improved it 
last year to select options based on the socket type but more is needed 
to handle socket options that are specific to connecting or listening 
sockets. As things stand, the Solaris specific SO_FLOW_SLA option is the 
only one with this complication and it is currently special cased by 
PlainSocketImpl. I want to push this special casing to 
ExtendSocketOptions so that the special handing is in one place.

The proposed changes are here:
   http://cr.openjdk.java.net/~alanb/8217451/webrev/index.html

-Alan