Updating the LF MPMC queue and replacing DirQueue with it

Making the MPMC queue support when producers are consumers at the same
time by adding a variable work, mpmc_push_work() that increments work
and mpmc_task_done() that decrements work, and if work = 0 calls
mpmc_producers_finished() that pushes poinsons to wake up sleeping
threads and make them return NULL

Replacing DirQueue, a queue growable with realloc with the MPMC queue

platform.h

@@ -45,35 +45,12 @@ static double timer_stop(HiResTimer *t) {
          (double)g_qpc_freq.QuadPart;
 }
 
-/* Scan folders */
-
-typedef struct DirQueue DirQueue;
-
-typedef struct DirQueue {
-  char **items;
-  size_t count;
-  size_t cap;
-  size_t active;
-
-  int stop;
-
-#if PLATFORM_WINDOWS
-  CRITICAL_SECTION cs;
-  CONDITION_VARIABLE cv;
-#else
-  pthread_mutex_t mutex;
-  pthread_cond_t cond;
-#endif
-} DirQueue;
-
-// MPMC Queue
+// Workers context
 
 static MPMCQueue g_dir_queue;
 static MPMCQueue g_file_queue;
 
 typedef struct {
-  DirQueue *dir_queue;
-
   mem_arena *path_arena;
   mem_arena *meta_arena;
 } ScannerContext;
@@ -81,7 +58,3 @@ typedef struct {
 typedef struct {
   mem_arena *arena;
 } WorkerContext;
-
-// void scan_folder_windows_parallel(const char *base, ScannerContext *ctx);
-// void scan_folder_posix_parallel(const char *base, ScannerContext *ctx);
-//