Ben changed the icon names to a naming scheme using org.fsf.xxx
The changes were missing in the windows build resulting in a
build failure for the windows target.
EXTRA_DIST += $(top_srcdir)/src/ui/gui/artwork/splash.svg $(icons) $(icon_srcs)
-src/ui/gui/icons/pspp.ico: src/ui/gui/icons/16x16/apps/pspp.png src/ui/gui/icons/32x32/apps/pspp.png src/ui/gui/icons/48x48/apps/pspp.png src/ui/gui/icons/256x256/apps/pspp.png
+src/ui/gui/icons/pspp.ico: src/ui/gui/icons/16x16/apps/org.fsf.pspp.png src/ui/gui/icons/32x32/apps/org.fsf.pspp.png src/ui/gui/icons/48x48/apps/org.fsf.pspp.png src/ui/gui/icons/256x256/apps/org.fsf.pspp.png
$(MKDIR_P) ${@D}
convert $^ $@