Double union quiet NaN notes

src/duk_dblunion.h.in

@@ -203,7 +203,7 @@ typedef union duk_double_union duk_double_union;
  *
  *  When packed duk_tval is used, the NaN space is used to store pointers
  *  and other tagged values in addition to NaNs.  Actual NaNs are normalized
- *  to a specific format.  The macros below are used by the implementation
+ *  to a specific quiet NaN.  The macros below are used by the implementation
  *  to check and normalize NaN values when they might be created.  The macros
  *  are essentially NOPs when the non-packed duk_tval representation is used.
  *
@@ -211,7 +211,8 @@ typedef union duk_double_union duk_double_union;
  *  the packed duk_tval and works correctly for all NaNs except those that
  *  begin with 0x7ff0.  Since the 'normalized NaN' values used with packed
  *  duk_tval begin with 0x7ff8, the partial check is reliable when packed
- *  duk_tval is used.
+ *  duk_tval is used.  The 0x7ff8 prefix means the normalized NaN will be a
+ *  quiet NaN regardless of its remaining lower bits.
  *
  *  The ME variant below is specifically for ARM byte order, which has the
  *  feature that while doubles have a mixed byte order (32107654), unsigned