Compile fails using gcc version 4.2.3.  ./configure completes with apparent success, but make fails with the following:

root:# make
make  all-recursive
make[1]: Entering directory `/home/tigerwolf/Downloads/xfce4-netload-plugin-1.0.0'
Making all in panel-plugin
make[2]: Entering directory `/home/tigerwolf/Downloads/xfce4-netload-plugin-1.0.0/panel-plugin'
gcc -DHAVE_CONFIG_H -I. -I..   -DNDEBUG -DPACKAGE_LOCALE_DIR=\"/usr/local/share/locale\" -I/usr/include/xfce4/ -I/usr/X11R6/include -I/usr/include/xfce4 -I/usr/include/gtk-2.0 -I/usr/lib/gtk-2.0/include -I/usr/include/pango-1.0 -I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include -I/usr/include/cairo -I/usr/include/freetype2 -I/usr/include/atk-1.0 -I/usr/local/include/libpng12 -I/usr/X11R6/include -I/usr/include/xfce4 -I/usr/include/gtk-2.0 -I/usr/lib/gtk-2.0/include -I/usr/include/pango-1.0 -I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include -I/usr/include/cairo -I/usr/include/freetype2 -I/usr/include/atk-1.0 -I/usr/local/include/libpng12   -O2 -march=i586 -mtune=i686 -MT xfce4_netload_plugin-netload.o -MD -MP -MF .deps/xfce4_netload_plugin-netload.Tpo -c -o xfce4_netload_plugin-netload.o `test -f 'netload.c' || echo './'`netload.c
netload.c:347: error: expected declaration specifiers or '...' before 'GtkTooltip'
netload.c: In function 'tooltip_cb':
netload.c:349: error: 'tooltip' undeclared (first use in this function)
netload.c:349: error: (Each undeclared identifier is reported only once
netload.c:349: error: for each function it appears in.)
make[2]: *** [xfce4_netload_plugin-netload.o] Error 1
make[2]: Leaving directory `/home/tigerwolf/Downloads/xfce4-netload-plugin-1.0.0/panel-plugin'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/home/tigerwolf/Downloads/xfce4-netload-plugin-1.0.0'
make: *** [all] Error 2