[rand.req.seedseq] Rephrase in terms of const types not values

Author: jwakely

source/numerics.tex

@@ -1656,9 +1656,9 @@
     \tcode{T} is the type named by
     \tcode{S}'s associated \tcode{result_type};
   \item
-    \tcode{q} is a value of \tcode{S}
+    \tcode{q} is a value of type \tcode{S}
     and
-    \tcode{r} is a possibly const value of \tcode{S};
+    \tcode{r} is a value of type \tcode{S} or \tcode{const S};
   \item
     \tcode{ib} and \tcode{ie} are input iterators
     with an unsigned integer \tcode{value_type} of at least 32 bits;