[PD] documenting messages to/from Pd and dynamic patching

[João Pais]

I don't see a mention to these messages: mouse, mouseup, mousedown, 
relocate. And also all other messages related to gui stuff.

It could also be clearly mentioned that subpatches receive messages sent 
to pd-[subpatch], and abstractions are named [abstraction].pd (if I'm 
recalling correctly) - unless there is a namecanvas used in those.


> People, I'm on a roll here, updating much of the help files and 
> documentation.
>
> I just hit an important new addition, documenting "Messages to/from 
> Pd" and "Dynamic Patching"
>
> I'd like you people to revise it.
>
> Here's the commit => 
> https://github.com/pure-data/pure-data/pull/1455/commits/0ec5429629eb1045c901ab9c74befd124ccb6e69
>
> already in an open PR
>
> Cheers