Make sure hack doesn't stick around

[mjschultz]

See #2 for the self-described hack.

There is some crazy interaction between the terminal, pc emulator, and the Xinu kernel. This is technically a Xinu bug (probably), but manifests in the js emulator, so I'm putting the issue here.

From the fix in #2, the problem is somewhere in the IRQ handler (programmable interrupt controller code) or how UART/serial-specific interrupts are handled/cleared.

My notes:

• uart ends up in fifo mode, despite xinu saying not fifo mode
  • the change happens during platforminit
• set_irq_func(0) (de-assert irq?) then set_irq_func(1) (assert irq?) forces transmission
• presumably the js serial code expects a certain condition and Xinu is not meeting it
• possibly in irq handling, but since the de-assert/assert trick works it seems more uart related
• what does Xinu have to do to meet the right conditions to cause the irq to de-assert/re-assert?