[master] make sure static.zone is generated for new AUTHORS or version string.

previously, once this zone file was generated, incremental build
(i.e., 'make' without 'make clean') may fail to update this file.
that would result in unexpected answer from b10-auth for *.bind
quieries, and would also cause unittest failures in auth/tests.

okayed on jabber.

src/lib/datasrc/Makefile.am

@@ -12,7 +12,9 @@ pkglibdir = $(libexecdir)/@PACKAGE@/backends
 datasrc_config.h: datasrc_config.h.pre
 	$(SED) -e "s|@@PKGLIBDIR@@|$(pkglibdir)|" datasrc_config.h.pre >$@
 
-static.zone: static.zone.pre
+# The top config.h defines "PACKAGE_STRING".  When it's changed we neeed to
+# regenerate this zone file.
+static.zone: static.zone.pre $(top_builddir)/config.h $(top_srcdir)/AUTHORS
 	$(SED) -e "s|@@VERSION_STRING@@|$(PACKAGE_STRING)|" $(srcdir)/static.zone.pre >$@
 	$(SED) -e 's/\(.*\)/AUTHORS.BIND.	0	CH	TXT	"\1"/' $(top_srcdir)/AUTHORS >>$@