Packet debugging is extremely slow

Enabling packet debugging slows down MUSHclient tremendously. It makes it pretty hard to track problems that appear after hundreds of lines that are dependent on timing. It shouldn't be this slow to just dump some text.

This is a side-effect of the fact that the notepad windows (such as used by the packet debugging) are implemented as a windows text control and they are very slow when the text gets large. I think this is partly because every time there is new text the control attempts to wordwrap the entire contents again.

I have added a new plugin callback "OnPluginPacketDebug" to the pre-release version that lets you control how the debugging is displayed. For example, you could write it to a file.