Updated TODO and "optimized" build settings

Signed-off-by: Olli Vanhoja <olli.vanhoja@ninjaware.fi>
Implemented child thread deletion code on thread exit

Signed-off-by: Olli Vanhoja <olli.vanhoja@ninjaware.fi>
Thread deletion on exit is now implemented completely in kernel context (which enables portability to a processor models with privileged modes)
ie. Deletion on thread exit is made by only using syscalls/sw interrupts.

Signed-off-by: Olli Vanhoja <olli.vanhoja@ninjaware.fi>