x86_64 is used as a baseline: the "x86_64" entry, whatever status it has,
is transformed into "all", and then the other entries in ARCHITECTURES
either dropped or rearranged appropriately.
* BUILD was no longer working. We could have replaced "automake" by
"automake --add-missing" but it was easier to switch to autoreconf.
* Switch HOMEPAGE and SOURCE_URI to https.