parallelize tests via the native go mechanism

Makefile

@@ -21,20 +21,8 @@ capdefs:
 
 test:
 	python3 ./gencapdefs.py | diff - ${capdef_file}
-	cd irc && go test . && go vet .
-	cd irc/caps && go test . && go vet .
-	cd irc/cloaks && go test . && go vet .
-	cd irc/connection_limits && go test . && go vet .
-	cd irc/email && go test . && go vet .
-	cd irc/flatip && go test . && go vet .
-	cd irc/history && go test . && go vet .
-	cd irc/isupport && go test . && go vet .
-	cd irc/migrations && go test . && go vet .
-	cd irc/modes && go test . && go vet .
-	cd irc/mysql && go test . && go vet .
-	cd irc/passwd && go test . && go vet .
-	cd irc/sno && go test . && go vet .
-	cd irc/utils && go test . && go vet .
+	go test ./...
+	go vet ./...
 	./.check-gofmt.sh
 
 smoke: