patch applied (packages/unix): in pPrPr_disableITimers (who made up that name?) call the RTS to disable the timer

[Simon Marlow]

Wed Sep 12 07:56:47 PDT 2007  Simon Marlow <simonmar at microsoft.com>
  * in pPrPr_disableITimers (who made up that name?) call the RTS to disable the timer
  Since we switched to using timer_create() in the RTS, this function
  has been failing to disables the timer interrupts.  This turns out to
  be the cause of the random framework failures in the test suite.
  Invoking the RTS to turn off the timer signal is the right thing.

    M ./cbits/execvpe.c -12 +7