Fix ASSIGN_DBL on Win64

We were comparing ALIGNMENT_DOUBLE to ALIGNMENT_LONG, but really
we cared about W_ values, and sizeof(long) /= sizeof(void *) on Win64

includes/Stg.h

@@ -257,7 +257,7 @@ typedef StgFunPtr       F_;
 INLINE_HEADER void     ASSIGN_FLT (W_ [], StgFloat);
 INLINE_HEADER StgFloat    PK_FLT     (W_ []);
 
-#if ALIGNMENT_FLOAT <= ALIGNMENT_LONG
+#if ALIGNMENT_FLOAT <= ALIGNMENT_VOID_P
 
 INLINE_HEADER void     ASSIGN_FLT(W_ p_dest[], StgFloat src) { *(StgFloat *)p_dest = src; }
 INLINE_HEADER StgFloat PK_FLT    (W_ p_src[])                { return *(StgFloat *)p_src; }
@@ -278,9 +278,9 @@ INLINE_HEADER StgFloat PK_FLT(W_ p_src[])
     return(y.f);
 }
 
-#endif /* ALIGNMENT_FLOAT > ALIGNMENT_LONG */
+#endif /* ALIGNMENT_FLOAT > ALIGNMENT_VOID_P */
 
-#if ALIGNMENT_DOUBLE <= ALIGNMENT_LONG
+#if ALIGNMENT_DOUBLE <= ALIGNMENT_VOID_P
 
 INLINE_HEADER void     ASSIGN_DBL (W_ [], StgDouble);
 INLINE_HEADER StgDouble   PK_DBL     (W_ []);
@@ -288,7 +288,7 @@ INLINE_HEADER StgDouble   PK_DBL     (W_ []);
 INLINE_HEADER void      ASSIGN_DBL(W_ p_dest[], StgDouble src) { *(StgDouble *)p_dest = src; }
 INLINE_HEADER StgDouble PK_DBL    (W_ p_src[])                 { return *(StgDouble *)p_src; }
 
-#else /* ALIGNMENT_DOUBLE > ALIGNMENT_LONG */
+#else /* ALIGNMENT_DOUBLE > ALIGNMENT_VOID_P */
 
 /* Sparc uses two floating point registers to hold a double.  We can
  * write ASSIGN_DBL and PK_DBL by directly accessing the registers