avoid collision with major/minor in types.h

Index: layers/vulkan/generated/vk_extension_helper.h
--- layers/vulkan/generated/vk_extension_helper.h.orig
+++ layers/vulkan/generated/vk_extension_helper.h
@@ -74,6 +74,12 @@ Times to NOT use it
 
 #define VVL_UNRECOGNIZED_API_VERSION 0xFFFFFFFF
 
+#ifdef __OpenBSD__
+// collision with types.h
+#undef major
+#undef minor
+#endif
+
 class APIVersion {
   public:
     APIVersion() : api_version_(VVL_UNRECOGNIZED_API_VERSION) {}
