Test case based on a patch by Guo Jian.

This is of course a fairly naive initial implementation. We'd probably want to
batch up drawing operations, and only execute them on EndDraw() or Flush() to
reduce state setup overhead.

Aggregates are returned through an implicit parameter after the this/interface
pointer. Note that this follows the C++ convention, affected methods are not
callable from C with the Microsoft headers.

kernel32/tests: Add tests for partially received pipe messages after calling SetNamedPipeHandleState.