Merge branch 'Mutex_trylock_adding_missing_count_parameter' of git://github.com/dmaziec1/mbed-os into dev_rollup

Author: 0xc0170

rtos/source/Mutex.cpp

@@ -97,6 +97,7 @@ bool Mutex::trylock_for(uint32_t millisec)
 {
     osStatus status = osMutexAcquire(_id, millisec);
     if (status == osOK) {
+        _count++;
         return true;
     }