Clean up threading

* Rename everything.
    * Strip J prefix.
    * Change UpperCamelCase functions to lowerCamelCase.
  * Remove global (!) semaphore count mutex on OSX.
  * Remove semaphore count getter (unused, unsafe, depended on internal
    API functions on Windows, and used a hack on OSX).
  * Add `Atomic<type>`.
  * Make `Thread` handle thread names.
  * Add support for C++11 multi-threading.
  * Combine pthread and win32 sources.
  * Remove `ThreadStarted` (unused, unneeded).
  * Move some includes from the headers to the sources.
  * Move all of `Event` into its header (allows inlining with no new includes).
  * Make `Event` use `Semaphore` (except on Windows).
  * Move some porting functions into `Thread`.
  * Integrate logging with `Thread`.
  * Add threading test.

src/emerge.h

@@ -86,7 +86,7 @@ public:
 	std::set<u32> gen_notify_on_deco_ids;
 
 	//// Block emerge queue data structures
-	JMutex queuemutex;
+	Mutex queuemutex;
 	std::map<v3s16, BlockEmergeData *> blocks_enqueued;
 	std::map<u16, u16> peer_queue_count;