Make the behaviour more consistent by using the standard gnome
autogen.sh from https://wiki.gnome.org/Projects/GnomeCommon/Migration

.
This makes autogen correctly behave when NOCONFIGURE is set amongst
other things.

Also stop generating README/INSTALL (autotools will install a standard
INSTALL file)

Reviewed-by: Justin Kim <justin.kim@collabora.com>
Signed-off-by: Sjoerd Simons <sjoerd.simons@collabora.co.uk>
Differential Revision: https://phabricator.apertis.org/D2057