contrib: add gecko headers

contrib/src/gecko/rules.mak

+# gecko (mozilla plugin headers)
+
+PKGS += gecko
+
+NPAPI_HEADERS_SVN_URL := http://npapi-sdk.googlecode.com/svn/trunk/headers
+NPAPI_HEADERS_SVN_REV := HEAD # revision number, or just HEAD for the latest
+
+$(TARBALLS)/gecko-svn.tar.xz:
+	rm -Rf gecko-svn
+	$(SVN) export $(NPAPI_HEADERS_SVN_URL) gecko-svn -r $(NPAPI_HEADERS_SVN_REV)
+	tar cvJ gecko-svn > $@
+
+.sum-gecko: gecko-svn.tar.xz
+	$(warning Integrity check skipped.)
+	touch $@
+
+gecko: gecko-svn.tar.xz .sum-gecko
+	$(UNPACK)
+	$(MOVE)
+
+.gecko: gecko
+	cp $</*.h "$(PREFIX)/include"
+	touch $@