Fix compiler warnings for syscall-tester.

git-svn-id: svn://svn.code.sf.net/p/dmtcp/code/trunk@2813 ba6dc0ae-232f-0410-883f-9ebac64fc565
JSocket: return partial reads instead of failing.

git-svn-id: svn://svn.code.sf.net/p/dmtcp/code/trunk@2814 ba6dc0ae-232f-0410-883f-9ebac64fc565
Socket: Refill disconnected sockets.

For situations where t remote end of the socket is closed before data is
read from the local end.  In this case, the data is drained and later
refilled after the (dead) socket is restored.

Enhanced stale-fd test to capture related errors.

git-svn-id: svn://svn.code.sf.net/p/dmtcp/code/trunk@2815 ba6dc0ae-232f-0410-883f-9ebac64fc565