XFCE4_GUI_CFLAGS, XFCE4_GUI_LIBS, XFCE4_GUI_XFCE4_GUI_REQUIRED_VERSION, and
probably others are not being substituted by configure into the Makefile's in
xfce4-mixer's subdirectories. As a result, CVS fails to build.

The XFCE4_GUI_CFLAGS problem shows itself as gcc saying 
gcc: cannot specify -o with -c or -S and multiple compilations

(The problem is that there's a @XFCE4_GUI_CFLAGS@ in the command line which is
seen by gcc as an additional file name.)

If I manually edit the configure script to substitute the XFCE4_GUI_CFLAGS,
XFCE4_GUI_LIBS, and XFCE4_GUI_XFCE4_GUI_REQUIRED_VERSION variables, I still get

xfce4_mixer-xfce-mixer-window.o: In function `xfce_mixer_window_set_my_icon':
/usr/local/archives/checkouts/xfce4/xfce4-mixer/src/mixer-window.gob:108:
undefined reference to `xfce_icon_theme_get_for_screen'
/usr/local/archives/checkouts/xfce4/xfce4-mixer/src/mixer-window.gob:110:
undefined reference to `xfce_icon_theme_load_category'
collect2: ld returned 1 exit status
make[2]: *** [xfce4-mixer] Error 1
make[2]: Leaving directory `/usr/local/archives/checkouts/xfce4/xfce4-mixer/src'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/usr/local/archives/checkouts/xfce4/xfce4-mixer'
make: *** [all] Error 2