[PATCH] fix fdi DTD and validate fdi's

[Artem Kachitchkine]

Sorry folks that I messed up distcheck, will be more diligent next time.

Depending on HAL's policy towards fancy gmake features, the patch could 
have simply been:

-    xmllint --noout --dtdvalid $(top_srcdir)/fdi/fdi.dtd $(dist_fdi_DATA)
+    xmllint --noout --dtdvalid $(top_srcdir)/fdi/fdi.dtd $(addprefix 
$(srcdir)/, $(dist_fdi_DATA))

I can prepare a patch, if you think it's worth it.

-Artem.