RFR [13] 8219446: Specify behaviour of timeout accepting methods of Socket and ServerSocket if timeout is negative

[Chris Hegarty]

This review request is for a specification only change. It clarifies the
behaviour of the timeout accepting methods of Socket and ServerSocket,
when the given a negative timeout. A negative timeout value will result
in an IllegalArgumentException being thrown.

These methods already throw IllegalArgumentException, so this change is
effectively documenting existing long-standing behaviour.

Note: Before this change, ServerSocket::setSoTimeout defers the timeout
argument checking to its socket impl. The default plain socket impl
throws IllegalArgumentException if given a negative timeout. It is
possible, but unlikely, that an alternative custom socket impl could
have accepted a negative timeout, but the effects of such are
unspecified and unknown. After this change, ServerSocket will no longer
defer the timeout argument checking, it will check its own arguments.

Webrev:
   http://cr.openjdk.java.net/~chegar/8219446/webrev.00/
CSR:
   https://bugs.openjdk.java.net/browse/JDK-8221248

-Chris.