autogen.sh: Obey the ACLOCAL_FLAGS environment variable
autogen.sh: Obey the ACLOCAL_FLAGS environment variable

This allows additional macro search paths to be searched by setting
the ACLOCAL_FLAGS variable. This is needed for jhbuild.

http://bugzilla.openedhand.com/show_bug.cgi?id=2039

ZachGoldberg/gupnp-gi,ZachGoldberg/gupnp-gi,GNOME/gupnp,GNOME/gupnp,GNOME/gupnp,ZachGoldberg/gupnp-gi,GNOME/gupnp