[Lazarus] WriteLn back to the GUI

[ListMember]

Hello,

I am trying to find where WriteLn is declared; but, apparently, WriteLn 
is among the select few that Lazarus will ignore 'Find Declaration' 
requests --at least that's how it behaves (latest Lazarus stable) on my 
side.

My ultimate goal, after finding where it is declared, is to locally 
modify that part of the sources so that (instead of writing to the 
console) it will use a global callback to display whatever WriteLn'ed in 
a TMemo.

Or, is there already an alternative to redirect console output to the 
running GUI?