win32: close the handles associated with a spawned child process

Probably not a big deal because at this point, the call is only used when
spawning a daemonized server.  In that case, the parent process goes away first,
so it won't prevent the child from being cleaned up.

mercurial/win32.py

@@ -588,6 +588,9 b' def spawndetached(args):'
     if not res:
         raise ctypes.WinError()
 
+    _kernel32.CloseHandle(pi.hProcess)
+    _kernel32.CloseHandle(pi.hThread)
+
     return pi.dwProcessId
 
 def unlink(f):