By now the scheduling timer was only refreshed for a new scheduling timeout
when the choosen scheduling context has changed. But we want it to be refreshed
also when the scheduled context yields without an effect to the schedulers
choice (this is the case e.g. when the idle thread gets a scheduling timeout
or a thread yields without any competitor in its priority band).
ref #1151
This patch changes the top-level directory layout as a preparatory
step for improving the tools for managing 3rd-party source codes.
The rationale is described in the issue referenced below.
Issue #1082
