- Refactor mthread structure fields to prevent name clashes

- Remove sanity checks for initialized mutexes and condition variables. This
  significantly boosts performance. The checks can be turned back on by
  compiling libmthread with MTHREAD_STRICT. According to POSIX operations on
  uninitialized variables are a MAY fail if, therefore allowing this
  optimization.
- Test59 has to be accommodated to the lack of sanity checks on uninitialized
  variables in the library. It specifically tests for them and will run into
  segfaults when the checks are absent in the library.
- Fix a few bugs related to the scheduler
- Do some general code cleanups

lib/libmthread/queue.c

@@ -21,10 +21,10 @@ mthread_thread_t thread;
   last = mthread_find_tcb(thread);
 
   if (mthread_queue_isempty(queue)) {
-  	queue->head = queue->tail = last;
+  	queue->mq_head = queue->mq_tail = last;
   } else  {
-	queue->tail->m_next = last;
-	queue->tail = last;	/* 'last' is the new last in line */
+	queue->mq_tail->m_next = last;
+	queue->mq_tail = last;	/* 'last' is the new last in line */
   }
 }
 
@@ -37,7 +37,7 @@ mthread_queue_t *queue;		/* Queue that has to be initialized */
 {
 /* Initialize queue to a known state */
 
-  queue->head = queue->tail = NULL;
+  queue->mq_head = queue->mq_tail = NULL;
 }
 
 
@@ -47,7 +47,7 @@ mthread_queue_t *queue;		/* Queue that has to be initialized */
 PUBLIC int mthread_queue_isempty(queue)
 mthread_queue_t *queue;
 {
-  return(queue->head == NULL);
+  return(queue->mq_head == NULL);
 }
 
 
@@ -64,8 +64,8 @@ mthread_queue_t *queue;
 #ifdef MDEBUG
   printf("Dumping queue: ");
 #endif
-  if(queue->head != NULL) {
-  	t = queue->head;
+  if(queue->mq_head != NULL) {
+  	t = queue->mq_head;
 	if (t == &mainthread) tid = MAIN_THREAD;
 	else tid = t->m_tid;
 #ifdef MDEBUG
@@ -106,18 +106,18 @@ mthread_queue_t *queue;		/* Queue we want a thread from */
   mthread_tcb_t *tcb;
 
   /* Calculate thread id from queue head */
-  if (queue->head == NULL) thread = NO_THREAD;
-  else if (queue->head == &mainthread) thread = MAIN_THREAD;
-  else thread = (queue->head->m_tid);
+  if (queue->mq_head == NULL) thread = NO_THREAD;
+  else if (queue->mq_head == &mainthread) thread = MAIN_THREAD;
+  else thread = (queue->mq_head->m_tid);
 
   if (thread != NO_THREAD) { /* i.e., this queue is not empty */
-  	tcb = queue->head;
-	if (queue->head == queue->tail) {
+  	tcb = queue->mq_head;
+	if (queue->mq_head == queue->mq_tail) {
 		/* Queue holds only one thread */
-		queue->head = queue->tail = NULL; /* So mark thread empty */
+		queue->mq_head = queue->mq_tail = NULL; /* So mark thread empty */
 	} else {
 		/* Second thread in line is the new first */
-		queue->head = queue->head->m_next;
+		queue->mq_head = queue->mq_head->m_next;
 	}
 
 	tcb->m_next = NULL; /* This thread is no longer part of a queue */