IOCP: CTRL_CLOSE_EVENT, CREATE_NO_WINDOW, KILL_ON_JOB_CLOSE and sync-handle semantics #11

Windows process and console semantics that differ from Node/libuv, found in the PR #5 review (item 9):

• CTRL_CLOSE_EVENT: the console handler returns TRUE for it (signals.rs), so handlers registered earlier by the host never run and the process terminates immediately. Hup being best-effort is documented; skipping host handlers is not.
• CREATE_NO_WINDOW: it is unconditional (process.rs). Children that should share the console no longer receive Ctrl+C from the terminal, unlike Node.
• KILL_ON_JOB_CLOSE: it kills grandchildren when the job is released, even after the leader exited normally. On Unix they would survive.
• Duplex synchronous handles share one FIFO for reads and writes, so an idle read blocks every write.
• integration.rs: it reports a pump error once, then the loop stalls and Drop spins.

Each needs a decision (match Node, or document the difference) and a Windows test.