new-style mysql authentication in pure ruby

ruby has two modules for connecting to mysql. one is called mysql/ruby and is built in top of the standard libmysqlclient c library. the other is called ruby/mysql and is pure ruby. the problem with the latter is that it is a from-scratch implementation of the mysql network protocol, and the authentication handshake changed in mysql 4.1.

but here is a patch to add support for new-style mysql authentication to ruby/mysql. it should also deal with the other protocol changes that came along at the same time. it doesn’t do anything to expose server-side prepared statements.

it is only lightly tested. in particular, i haven’t tried to connect to a pre-4.1 version of the server. it should still work, but it is entirely possible i screwed it up. i’m also still just learning ruby, so there are some ugly bits.

i think having more from-scratch implementations of the protocol is a good thing. there’s at least five — the server code itself (and client library), connector/j, connector/net, ruby/mysql, and Net::MySQL (perl). once we have these all collected into an integration test suite, the server developers will get much better feedback when they go off the reservation with the protocol.