"Extension" versus "module"

Appendix F (contrib.sgml and its subsidiary files) is pretty consistent
about using "module" to refer to a contrib, uh, module.

I considered doing a search-and-replace to change this to "extension",
but I'm not convinced that's a good idea. I think "extension" means a
specific kind of SQL object that we just invented, and it's not exactly
the same concept as "one of those subdirectories under contrib/". One
pretty obvious example is that contrib/spi calls itself a module, and
it's definitely not an extension --- it contains five extensions, none
of them named "spi". Another problem is that we'd like to speak of
upgrading a module from pre-9.1 to 9.1, and in only one of those two
states is it strictly correct to call it an "extension". But in some
sense it's still the same entity.

So I'm not sure whether to change the text at all. Comments?

regards, tom lane