Plugin: Remove __socketAddressFactory() and toString() on SocketAddresses

Plugin: Remove __socketAddressFactory() and toString() on SocketAddresses

In order for NaCl to work in Chromium's Mac sandbox and Linux seccomp
sandbox, we need to remove the ability to convert SocketAddress
descriptors to strings and back again.

The first step is to remove the interfaces that are exposed to web
apps via the plugin.  After this we will change the implementation of
SocketAddress and BoundSocket descriptors.

BUG=http://code.google.com/p/nativeclient/issues/detail?id=344

Committed: http://code.google.com/p/nativeclient/source/detail?r=2656

[Mark Seaborn, 2010-07-12 14:53:54]

Mark S persuaded me to take on another piece of work...

[Mark Schneckloth, 2010-07-12 17:59:46]

LGTM