Yahoo Japan Removal

[Michael McConville]

I just committed the removal of Yahoo Japan to my repo:

	https://hg.pidgin.im/soc/2015/mmcc/main/rev/0cf05a71fef7

Here's the ticket:

	https://developer.pidgin.im/ticket/15906

As mentioned in the ticket comments, the protocol is confirmed dead.

Last I tested, it compiles without warnings and runs. I successfully
tested a Yahoo chat as well.

If someone has the time, reviewing it and merging it into pidgin/main
soon is probably a good idea. It contains a ton of repetitive
boilerplate removal and a lot of small diffs, so dealing with merge
conflicts could be painful.