Oops, forgot REPR stub in last commit.

src/pmc/repr.pmc

@@ -0,0 +1,8 @@
+/* A representation is responsible for object layout. Representations
+ * all fill out a REPR struct and maybe have one of their own with some
+ * extra bits of information in it. This PMC is simply a wrapper around
+ * a REPR for the purposes of GC, etc. It's up to the REPR to set the
+ * PMC up as it wishes. */
+pmclass REPR manual_attrs dynpmc group nqp {
+    /* XXX Needs custom mark/destroy implementing. */
+}