Wasm: Register a new WebAssembly language module type.

This is the first patch in adding WebAssembly language module support.

This just adds a new NXT_APP_WASM type, required by subsequent commits.

Reviewed-by: Alejandro Colomar <alx@nginx.com>
Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

src/nxt_router.c

@@ -280,6 +280,7 @@ static const nxt_str_t  *nxt_app_msg_prefix[] = {
     [NXT_APP_PERL]      = &http_prefix,
     [NXT_APP_RUBY]      = &http_prefix,
     [NXT_APP_JAVA]      = &empty_prefix,
+    [NXT_APP_WASM]      = &empty_prefix,
 };