internal/reflectlite, reflect: move StringHeader and SliceHeader back to package reflect

src/reflect/intw.go

@@ -0,0 +1,8 @@
+//go:build !avr
+
+package reflect
+
+// intw is an integer type, used in places where an int is typically required,
+// except architectures where the size of an int != word size.
+// See https://github.com/tinygo-org/tinygo/issues/1284.
+type intw = int