Forward declaration needed if DO_DER is defined.
autotools tweaks

configure.ac:
AM_INIT_AUTOMAKE should be idempotent, remove redundant invocation.
Integrate autoscan output.
Remove unnecessary AC_PATH_XTRA.

Makefile.am:
AUTOMAKE_OPTIONS=foreign is redundant: specified in configure.ac.
define DO_DER
define NE as the right kind of null; see http://bugs.debian.org/706636
Merge branch 'upstream'
bump standards version
tweak debian repo url according to today's scheme
log changes