Removed unused variables

When compiling with higher warning levels the compiler warns about
these unused variables.

Foundation/include/Poco/NamedMutex_UNIX.h

@@ -47,8 +47,6 @@ private:
 #if defined(sun) || defined(__APPLE__) || defined(__osf__) || defined(__QNX__) || defined(_AIX)
 	sem_t* _sem;
 #else
-	int _lockfd; // lock file descriptor
-	int _semfd;  // file used to identify semaphore
 	int _semid;  // semaphore id
 #endif
 };