[enumerated.types] Reword enumerated types

Also mention [re].

Author: frederick-vs-ja

source/lib-intro.tex

@@ -555,7 +555,7 @@
 \rSec4[enumerated.types]{Enumerated types}
 
 \pnum
-Several types defined in \ref{input.output} are
+Several types specified in \ref{input.output} and \ref{re} are
 \defnadjx{enumerated}{types}{type}.
 Each enumerated type may be implemented as an enumeration or as a synonym for
 an enumeration.