Makefile: add vet target

Makefile

 TEST?=./...
+VETARGS?=-asmdecl -atomic -bool -buildtags -copylocks -methods \
+         -nilfunc -printf -rangeloops -shift -structtags -unsafeptr
 
 default: test
 
@@ -10,6 +12,7 @@ dev:
 
 test:
 	go test $(TEST) $(TESTARGS) -timeout=10s
+	@$(MAKE) vet
 
 testrace:
 	go test -race $(TEST) $(TESTARGS)
@@ -17,4 +20,14 @@ testrace:
 updatedeps:
 	go get -d -v -p 2 ./...
 
-.PHONY: bin default test updatedeps
+vet:
+	@go tool vet 2>/dev/null ; if [ $$? -eq 3 ]; then \
+		go get golang.org/x/tools/cmd/vet; \
+	fi
+	@go tool vet $(VETARGS) . ; if [ $$? -eq 1 ]; then \
+		echo ""; \
+		echo "Vet found suspicious constructs. Please check the reported constructs"; \
+		echo "and fix them if necessary before submitting the code for reviewal."; \
+	fi
+
+.PHONY: bin default test updatedeps vet