Move the function "mbed_get_a9_tick_irqn()" declared in os_tick.h
to SysTimer.h so it does not get overridden when RTX is updated.
This function was originally added in:
3d3e89097d
Fixes for RZ_A1H issue 6543
OsEventObserver objects expect a context to be maintained per thread on
their behalf. Add this context to the thread control block and extend
the thread creation functions with the ability to supply a context.
OsEventObserver objects expect a context to be maintained per thread on
their behalf. Add this context to the thread control block and extend
the thread creation functions with the ability to supply a context.