a couple more tribute easter eggs

a couple more tribute easter eggs
 Changes to be committed:
	modified:   include/context.h
	modified:   include/extern.h
	modified:   src/files.c
	modified:   src/invent.c
	modified:   src/sounds.c
	modified:   src/spell.c

Add a couple more tribute easter eggs.

 - can lead to a remark by Death if you happen to have a pratchett book on
   your person, as suggested by M. Stephenson (fat chance you will, or
   think to #chat if you do, but it could be a tournament novelty or something
   obscure to strive for).
 - can draw some additional Death quotes from the tribute file. (There's two
   in there right now. If anyone wants to add or suggest some more, please go
   ahead. The Death quotes are at the end of the tribute file. One-liners
   only please or the code will only pull the last line.