Introduce Right Abstractions

Add correction of log of unittest of module pagecacheimpl.
Implement syncthread_t and syncrun_t

The implementation of type syncthread_t replaces type
exothread_t. A syncthread_t is a synchronous thread
which runs until it yields the processor -
see Wikipedia coroutines.

A syncthread_t will be used to handle multiple events and async I/O
per thread without need of locking.

The type syncrun_t replaces type exoscheduler_t
and offers a simple interface to create new synchronous
threads and to manage them in a run queue.

The type syncqueue_t extends queue_t with counting
and compacting memory.

The type syncwait_t is used to model a syncthread_t
waiting for the exit of another syncthread_t or any
other event.

The waiting thread waits on an event implemented as type
syncevent_t (also implemented in module syncwait.h).

The type syncwlist_t supports a list of syncevent_t
and therefore supports a list waiting threads (of type
syncwait_t).

-- Future --

In the future other mechanisms like semaphores
and message queues will be implemented using syncevent_t
and syncwlist_t.