Build-fix due to generation of include/click/config.h

autoreconf (autoheader) overrides config.h.in that was not originaly generated
using autoheader. Moved this code into include/click/config.h and generate
include/click/config-default.h based on config.h.in.

Signed-off-by: Gregory Detal <gregory.detal@uclouvain.be>