Relative includes

[Patrick McCarty]

Hello,

I am interested in the understanding how \include "..." is
implemented, since I want to figure out how to permit relative
includes and wildcards in pathnames.

My first attempts lead me to believe that this is implemented through
the lexer.  Is this correct?  Files such as lily/lexer.ll, and the
like.  If I can understand a little bit more about what is going on,
I'll try my best to work this out.

Thanks,
Patrick