Fix up linker flags

This adds LDFLAGS everywhere where they were previously pulled in via
other libraries. This is however unsupported by modern linkers.
You can trigger these failures by building with gold (or, I'm told, with
very new ld).

demos/Makefile.am

@@ -19,7 +19,9 @@ DEPS = 									\
 LDADDS = 								\
 	$(top_builddir)/gdk-pixbuf/libgdk_pixbuf-$(GTK_API_VERSION).la	\
 	$(top_builddir)/gdk/$(gdktargetlib)        			\
-	$(top_builddir)/gtk/$(gtktargetlib)
+	$(top_builddir)/gtk/$(gtktargetlib)				\
+	$(GTK_DEP_LIBS)							\
+	$(MATH_LIB)
 
 noinst_PROGRAMS = 		\
 	testpixbuf-drawable 	\