dynamically load qt graphics * configure.ac (QT_OPENGL_LIBS): New variable. (LIBOCTGUI_LINK_DEPS): Delete $OPENGL_LIBS from the list. * acinclude.m4 (OCTAVE_CHECK_QT_VERSION): Check for Qt OpenGL module separately from other Qt modules. * subst-cross-config-vals.in.sh, subst-config-vals.in.sh: Substitute it. * build-env.h, build-env.in.cc, toplev.cc: Include QT_OPENGL_LIBS in build info. * libgui/src/module.mk (%canon_reldir%_%canon_reldir%_la_CPPFLAGS): Delete -I$(srcdir)/libgui/graphics from the list. * __init_qt__.cc: Use DEFUN_DLD and DEFMETHOD_DLD macros. Include comment to register qt toolkit using PKG_ADD file. * libgui/graphics/module.mk: Build __init_qt__.oct. * libgui/module.mk (%canon_reldir%_liboctgui_la_LIBADD): Delete $(LIBOCTGUI_GRAPHICS_LIB) from the list. Use $(QT_LIBS) instead of $(LIBOCTGUI_LINK_DEPS). * main-window.cc: (octave_interpreter::octave_interpreter): Don't call install___init_qt___functions or register qt graphics toolkit. * run-octave.in: Add $builddir/libgui/graphics directory to LOADPATH.

--- a/build-aux/subst-cross-config-vals.in.sh	Mon Oct 15 15:27:36 2018 -0400
+++ b/build-aux/subst-cross-config-vals.in.sh	Fri Sep 28 18:18:09 2018 -0400
@@ -204,6 +204,7 @@
 QT_CPPFLAGS="@QT_CPPFLAGS@"
 QT_LDFLAGS="@QT_LDFLAGS@"
 QT_LIBS="@QT_LIBS@"
+QT_OPENGL_LIBS="@QT_OPENGL_LIBS@"
 RANLIB="@RANLIB@"
 RDYNAMIC_FLAG="@RDYNAMIC_FLAG@"
 READLINE_LIBS="@READLINE_LIBS@"
@@ -376,6 +377,7 @@
   -e "s|%OCTAVE_CONF_QT_CPPFLAGS%|\"${QT_CPPFLAGS}\"|" \
   -e "s|%OCTAVE_CONF_QT_LDFLAGS%|\"${QT_LDFLAGS}\"|" \
   -e "s|%OCTAVE_CONF_QT_LIBS%|\"${QT_LIBS}\"|" \
+  -e "s|%OCTAVE_CONF_QT_OPENGL_LIBS%|\"${QT_OPENGL_LIBS}\"|" \
   -e "s|%OCTAVE_CONF_RANLIB%|\"${RANLIB}\"|" \
   -e "s|%OCTAVE_CONF_RDYNAMIC_FLAG%|\"${RDYNAMIC_FLAG}\"|" \
   -e "s|%OCTAVE_CONF_READLINE_LIBS%|\"${READLINE_LIBS}\"|" | \