configure.ac: Drop maintainer mode, modernize libtool declarations
configure.ac: Drop maintainer mode, modernize libtool declarations

Use all arguments of AC_INIT.

AM_MAINTAINER_MODE is discouraged now, drop it.

Use LT_PREREQ and LT_INIT for libtool initialization instead of the older
declarations.

See https://live.gnome.org/GnomeGoals/ModernAutotools

pexip/pygobject,davibe/pygobject,davibe/pygobject,pexip/pygobject,sfeltman/pygobject,GNOME/pygobject,davibe/pygobject,sfeltman/pygobject,davibe/pygobject,GNOME/pygobject,GNOME/pygobject,pexip/pygobject,sfeltman/pygobject