more tweaks for the gui build * configure.ac (HAVE_QT, GUIDIR): New variables. Don't run qmake unless it is found. Don't check for moc, uic, or rcc unless qmake is available. List Qt headers and libraries in summary message. * Makefile.am (SUBDIRS): Add @GUIDIR@ to the list. * common.mk (do_subst_config_vals): Substitute OCTAVE_CONF_QT_INCDIR and OCTAVE_CONF_QT_LIBDIR. * gui/src/Makefile.am: Simplify pattern rule for moc files. (octave_gui_CPPFLAGS): = Include -I@QT_INCDIR@ in the list. (octave_gui_LDADD): Include ../../liboctave/liboctave.la and ../../libcruft/libcruft.la in the list. (libqterminal_la_CPPFLAGS): Include -I@QT_INCDIR@ in the list. * toplev.cc (octave_config_info): New struct fields, QT_INCDIR and QT_LIBDIR. * oct-conf.in.h (OCTAVE_CONF_QT_INCDIR, OCTAVE_CONF_QT_LIBDIR): New macros.