Always use PTHREAD_MUTEX_ERRORCHECK to create mutexes when -DDEBUG

Linux defines PTHREAD_MUTEX_ERRORCHECK = PTHREAD_MUTEX_ERRORCHECK_NP
anyway, so there's no need to special-case it.

rts/posix/OSThreads.c

@@ -107,11 +107,7 @@ initMutex(Mutex* pMut)
 #if defined(DEBUG)
     pthread_mutexattr_t attr;
     pthread_mutexattr_init(&attr);
-#if defined(linux_HOST_OS)
-    pthread_mutexattr_settype(&attr,PTHREAD_MUTEX_ERRORCHECK_NP);
-#else
     pthread_mutexattr_settype(&attr,PTHREAD_MUTEX_ERRORCHECK);
-#endif
     pthread_mutex_init(pMut,&attr);
 #else
     pthread_mutex_init(pMut,NULL);