Change handling of accepting socket connections

Change handling of accepting socket connections

The accept method have been removed from the ServerSocket class and
the signature for the connectionHandler callback have been changed to
provide the accepted socket as an argument.

This is to avoid the possibility for accept to return null even in the
case of pending connection. This could happen if an error like EAGAIN,
EWOULDBLOCK and EINTR was returned by it OS accept call and previously
there was no way of propagating this without returning null from the
Dart call to accept.

R=ager@google.com

BUG=
TEST=

Committed: https://code.google.com/p/dart/source/detail?r=1889

[Mads Ager (google), 2011-11-29 11:52:23]

lgtm