Port 'SignalMechanism' from 'Semaphore' to POSIX 'ConditionVariable' where possible

[elBoberido]

Brief feature description

The Semaphore supports only CLOCK_REALTIME, which has issues when the system time is changed. The POSIX ConditionVariable has an attribute to specify the clock and also accepts CLOCK_MONOTONIC.

On Systems that support POSIX condition variables, those should be used with the CLOCK_MONOTONIC instead of the Semaphore in combination with the AdaptiveWait.