Enforce valid tag syntax during input.

diff --git a/programs/winetest/winetest.h b/programs/winetest/winetest.h
index 79fd43e..2f2c58a 100644
--- a/programs/winetest/winetest.h
+++ b/programs/winetest/winetest.h
@@ -33,7 +33,8 @@
 void xprintf (const char *fmt, ...);
 char *vstrmake (size_t *lenp, va_list ap);
 char *strmake (size_t *lenp, ...);
-const char *badtagchar (const char *tag);
+int goodtagchar (char c);
+const char *findbadtagchar (const char *tag);
 
 int send_file (const char *name);