Issue #99 : withTouch() touchstart event was relying on direct access to...

Issue #99 : the withTouch() touchstart event handler was relying on direct access to the Processing.eventHandlers array to remove any existing mouse event handlers.

Instead of exposing Processing.eventHandlers array directly, this change exposes a method called detachEventHandlersByTypeMatch() which takes a regex of event types, iterates through the list of existing event handlers, and detaches the handlers that match.

The withTouch() touchstart handler then calls detachEventHandlersByTypeMatch() with a regex that matches the desired mouse events.
can you change the indent etc to match the code around it? Also note that "var" inside a for loop is meaningless because variable in Javascript are scoped to functions, not `{...}` blocks (like they would be in Java).
```
function detachEventHandlersByTypeMatch(types) {
  // Loop though eventHandlers and remove event listeners that match the given type regex
  for (var i = 0, ehl = eventHandlers.length, type; i < ehl; i++) {
    type = eventHandlers[i].type;
    if (type.match(types)) {
      detachEventHandler(eventHandlers[i]);
    }
  }
}
```