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/main.cpp

@@ -153,7 +153,7 @@ int main(int argc, char *argv[])
 	log_add_output_maxlev(&main_stderr_log_out, LMT_ACTION);
 	log_add_output_all_levs(&main_dstream_no_stderr_log_out);
 
-	log_register_thread("main");
+	log_register_thread("Main");
 
 	Settings cmd_args;
 	bool cmd_args_ok = get_cmdline_opts(argc, argv, &cmd_args);