make configure.ac automagically do the right thing on redhat 9

make configure.ac automagically do the right thing on redhat 9
remove crappy tolower() hack that was breaking the build on redhat 9
(because the kerberized openssl includes ctype.h)

before anyone yells at me, i did a little cvs archaeology on the tolower
thing, and it appears to have been in the Citadel source base since,
roughly, the Epoch. I doubt that the hack is needed any longer, and using
the OS's tolower() will handle extended charsets.

Anyone who is stupid enough to be using an OS with such a horribly broken
tolower() can just scratch their head and figure things out for
themselves. Citadel needs higher barriers to entry, there are too many
weirdos on the IGnet lately. :-)