(lib_LTLIBRARIES): Include libm17n-gui.la and

(lib_LTLIBRARIES): Include libm17n-gui.la and
libm17n-gd.la.
(OPTIONAL_LD_FLAGS): Include @FONTCONFIG_LD_FLAGS@.
(GUI_SOURCES): Delete it.
(libm17n_X_la_SOURCES): Don't include ${GUI_SOURCES}.
(libm17n_gui_la_SOURCES, libm17n_gui_la_LIBADD)
(libm17n_gui_la_LDFLAGS, libm17n_gd_la_SOURCES)
(libm17n_gd_la_LIBADD, libm17n_gd_la_LDFLAGS): New targets.
(linkgui_LDADD): Set to libm17n-gui.la
(linkgui_LDFLAGS): New target.
(SRC): Include ${libm17n_gui_la_SOURCES} and
${libm17n_gd_la_SOURCES}.