* This adds a new dependency on autoconf-archive.
* Pass WARN_CFLAGS/WARN_LDFLAGS/WARN_SCANNERFLAGS to everything we control the source of
* Disables all warning flags which make the build error out for now, we'll re-enable them
  in followup commits.
* AX_COMPILER_FLAGS is used with the release flag always on so we don't get
  -Werror by default.