configure: Drop AM_MAINTAINER_MODE

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
autogen.sh: Honor NOCONFIGURE=1

See http://people.gnome.org/~walters/docs/build-api.txt

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Merge branch 'master' of https://github.com/bbidulock/xdm