Use Rc<Cell> instead of passing `&mut irqs` all around.
The runtime impact is two additional size_t's per each holder of the
shared pointer.
Former-commit-id: afd3188c31608ebcf062256a7ad51575dbc90d8b
Former-commit-id: 22e0e01953968cee592b5408677e557059669c31
This test also caught a bug where hblank flag from the last
vblank-hblank would linger on the next HDraw.
Former-commit-id: b8916badc4bd874d9493229299150f6b2f00f5ed
Former-commit-id: 8ada7ccf3e65e7272d9bb828101520f1589cb4c4
One step closer for having green Travis checkmarks
Former-commit-id: eac65389e20e5c76804f6c086cae7078c1b51b8c
Former-commit-id: c891c75058dd47f6d59c674f1aeb8fc57436cab0