Added building of tweetnacl.diff to the Makefile

paper/Makefile

-SOURCES= code-tweetnacl.tex collection.bib conclusion.tex coq.tex highlevel.tex intro.tex lowlevel.tex preliminaries.tex proofs.tex rfc.tex t.bib tweetverif.tex
+SOURCES= code-tweetnacl.tex collection.bib conclusion.tex coq.tex highlevel.tex intro.tex lowlevel.tex preliminaries.tex proofs.tex rfc.tex t.bib tweetverif.tex tweetnacl.diff
 
 tweetverif.pdf: ${SOURCES}
 	pdflatex tweetverif.tex
@@ -6,6 +6,17 @@ tweetverif.pdf: ${SOURCES}
 	pdflatex tweetverif.tex
 	pdflatex tweetverif.tex
 
+
+tweetnacl.diff:
+	@echo $(BOLD)$(YELLOW)"Generating tweetnacl.diff"$(NO_COLOR)$(DARKGRAY)
+	diff -u ../proofs/vst/c/tweetnacl.c ../proofs/vst/c/tweetnaclVerifiableC.c > tweetnacl.diff.tmp; [ $$? -eq 1 ]
+	sed -i -e 1,2d tweetnacl.diff.tmp
+	echo '--- tweetnacl.c' >> tweetnacl.diff
+	echo '+++ tweetnaclVerifiableC.c' >> tweetnacl.diff
+	cat tweetnacl.diff.tmp >> tweetnacl.diff
+	rm tweetnacl.diff.tmp
+
+
 .PHONY: clean
 
 clean: