Sketch out C struct mappings for NQPRoutine and NQPSignature.

Author: jnthn

src/guts/multi_dispatch.h

@@ -1 +1,19 @@
-PMC *nqp_multi_dispatch(PARROT_INTERP, PMC *dispatcher, PMC *capture);
+/* This is how an NQPRoutine looks on the inside. */
+typedef struct {
+    PMC    *st;                 /* S-table, though we don't care about that here. */
+    PMC    *sc;                 /* Serialization context, though we don't care about that here. */
+    PMC    *_do;                /* Lower-level code object. */
+    PMC    *signature;          /* Signature object. */
+    PMC    *dispatchees;        /* List of dispatchees, if any. */
+    PMC    *dispatcher_cache;   /* Holder for any dispatcher cache. */
+} NQP_Routine;
+
+/* This is how an NQPSignature looks on the inside. */
+typedef struct {
+    PMC    *st;                 /* S-table, though we don't care about that here. */
+    PMC    *sc;                 /* Serialization context, though we don't care about that here. */
+    PMC    *types;              /* Set of types for arguments. */
+    PMC    *defindnesses;       /* Set of definedness flags for arguments. */
+} NQP_Signature;
+
+PMC *nqp_multi_dispatch(PARROT_INTERP, PMC *dispatcher, PMC *capture);