fix make locales

Makefile

@@ -21,14 +21,14 @@ messages.po: embroider*.py inkstitch.py
 .PHONY: locales
 locales:
 	# message files will look like this:
-	#   translations/messages-en_US.po
+	#   translations/messages_en_US.po
 	if ls translations/*.po > /dev/null 2>&1; then \
 		for po in translations/*.po; do \
-			lang=$${po%.po}; \
-			lang=$${lang#messages-}; \
+			lang=$${po%.*}; \
+			lang=$${lang#*_}; \
 			mkdir -p locales/$$lang/LC_MESSAGES/; \
 			msgfmt $$po -o locales/$$lang/LC_MESSAGES/inkstitch.mo; \
 		done; \
 	else \
-		mkdir locales; \
+		mkdir -p locales; \
 	fi