Added crouch toggle, global bool called isCrouch, function agent_toggle_down bound to toggle_down.

Shift+crouch=toggle, crouch doesn't work while toggle crouched, at the moment.
Formatted keys.ini to be completely aligned.

indra/newview/llappviewer.cpp

@@ -1098,6 +1098,8 @@ bool LLAppViewer::mainLoop()
 					&& !gFocusMgr.focusLocked())
 				{
 					joystick->scanJoystick();
+					if(isCrouch)
+						gAgent.moveUp(-1);
 					gKeyboard->scanKeyboard();
 				}