Drop old semaphore implementation

- Removed platform-specific implementations.
- Now all semaphores are in-object, unless they need to be conditionally created.
- Similarly to `Mutex`, provided a dummy implementation for when `NO_THREADS` is defined.
- Similarly to `Mutex`, methods are made `const` for easy use in such contexts.
- Language bindings updated: `wait()` and `post()` are now `void`.
- Language bindings updated: `try_wait()` added.

Bonus:
- Rewritten the `#ifdef` in `mutex.h` to meet the code style.

platform/windows/os_windows.cpp

@@ -48,7 +48,6 @@
 #include "drivers/windows/dir_access_windows.h"
 #include "drivers/windows/file_access_windows.h"
 #include "drivers/windows/rw_lock_windows.h"
-#include "drivers/windows/semaphore_windows.h"
 #include "drivers/windows/thread_windows.h"
 #include "joypad_windows.h"
 #include "lang_table.h"
@@ -228,7 +227,6 @@ void OS_Windows::initialize_core() {
 	borderless = false;
 
 	ThreadWindows::make_default();
-	SemaphoreWindows::make_default();
 	RWLockWindows::make_default();
 
 	FileAccess::make_default<FileAccessWindows>(FileAccess::ACCESS_RESOURCES);