Make sure implementors know which parse functions to use

[DanielOaks]

Generally, servers should perform all the nice accurate proper length checking and apply appropriate restrictions. Generally, clients (unless they need to for tech reasons like memory usage or using a language that requires strict limits) should accept whatever they can from the server and not try to be too pedantic about lengths (if there's some extra body or whatever to it then it's better to read it and not throw out valid data).

• ParseLine's comment should say "IRC clients should generally parse incoming lines using this function".
• ParseLineStrict's comment should say "IRC servers should generally parse incoming lines using this function".

These lines should be near the top so an implementor scrolling through sees at a glance which one they should look at.