Stop autoforward on BACKWARD key-press (#7417)

builtin/settingtypes.txt

@@ -115,7 +115,8 @@ safe_dig_and_place (Safe digging and placing) bool false
#    Enable random user input (only used for testing).
random_input (Random input) bool false

#    Continuous forward movement, toggled by autoforward key.
#    Continuous forward movement, toggled by autoforward key. 
#    Press the autoforward key again or the backwards movement to disable.
continuous_forward (Continuous forward) bool false

#    The length in pixels it takes for touch screen interaction to start.
@@ -147,6 +148,7 @@ joystick_frustum_sensitivity (Joystick frustum sensitivity) float 170
keymap_forward (Forward key) key KEY_KEY_W

#    Key for moving the player backward.
#    Will also disable autoforward, when active.
#    See http://irrlicht.sourceforge.net/docu/namespaceirr.html#a54da2a0e231901735e3da1b0edf72eb3
keymap_backward (Backward key) key KEY_KEY_S

src/game.cpp

@@ -1861,6 +1861,9 @@ void Game::processKeyInput()
		dropSelectedItem(isKeyDown(KeyType::SNEAK));
	} else if (wasKeyDown(KeyType::AUTOFORWARD)) {
		toggleAutoforward();
	} else if (wasKeyDown(KeyType::BACKWARD)) {
		if (g_settings->getBool("continuous_forward"))
			toggleAutoforward();
	} else if (wasKeyDown(KeyType::INVENTORY)) {
		openInventory();
	} else if (input->cancelPressed()) {