GHC Lexer

[Steffen Mazanek]

Hello,

to add a new keyword, say "struct" to 
the GHC, I have added ITstruct to data
type Token in module Lex.lhs. Further
on I have adapted ghcExtensionKeywordsFM.
Is this already sufficient for lexing? 
In LexCore there is a function lexKeyword 
without a comment. It is called by lexer 
if the first character is %. What does this
mean? 

Thank you,
Steffen