ww: implement package initialization

cmd/w6c/gc.h

@@ -60,6 +60,9 @@ struct Cg {
 				 * the bare-`main` carve-out: a dep's `fn main` must
 				 * mangle on its path like any decl; only the root
 				 * entry stays bare. */
+	const char *init_dispatch_symbol;	/* package-mode entry hook; the
+				 * root-owned dispatcher runs the complete reachable
+				 * package-init schedule before source main/test main. */
 };
 
 /* cgen.c */