configure curiosities

["Howard Chu" <hyc@highlandsun.com>]

These aren't vital questions to answer, but after examining the configure
and configure.in files, I got curious:
	why is the config.cache explicitly disabled?
	why is cc preferred over gcc?
	why is the install program explicitly checked, twice?

I think it's somewhat tedious to have to re-run the entire configure script
every time I want to enable or disable a single backend in slapd. Having all
of the tests cached would help speed this up a little.

In general I prefer gcc over whatever vendor-supplied cc is available (even
if the native compiler is already gcc; frequently I will have installed a
newer version than the OS distribution included). Are there known problems
with gcc that make cc the better choice?

There is an explicit check for BSD-compatible install script, but it is
already checked by default, so the identical test appears twice in the
configure script. I don't believe this is necessary. (Probably not harmful
either, but anything we can do to speed up the rebuild cycle is probably a
win.)