Initialize stack area in _NewContext()

Instead of initializing the stack (when INIT_STACKS is enabled) in start_task()
and _fiber_start(), do it in _NewContext().  This helps to both reduce code
duplication AND ensure that all contexts get an initialized stack (previously
the background/idle task's was missed).

Change-Id: If2d50309d2be48fac937f5d0ae96b9de185c0fe2
Signed-off-by: Peter Mitsis <peter.mitsis@windriver.com>
5 files changed