configure: drop various AC_macros

As of last commit we no longer create any binaries, thus config.h, CC
and libtool are no longer required.

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Acked-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Uli Schlachter <psychon@znc.in>