[m-rev.] diff: fix some errors in the reference manual

[Julien Fischer]

Fix some errors in the reference manual.

The first of these was pointed out by Fabrice Nicol.

doc/reference_manual.texi:
     Use the correct type in the descriptions of some existential type
     examples.

Julien.

diff --git a/doc/reference_manual.texi b/doc/reference_manual.texi
index 951517f..7f59c05 100644
--- a/doc/reference_manual.texi
+++ b/doc/reference_manual.texi
@@ -6921,7 +6921,7 @@ but the caller is allowed to depend on those type variables
  satisfying the declared type class constraints, if any.

  For example, the function @samp{make_list} constructs
-a value of type @samp{list_of_showable}
+a value of type @samp{showable_list}
  containing a sequence of values of different types,
  all of which are instances of the @samp{showable} class

@@ -6946,7 +6946,7 @@ applies the @samp{show} method of the @samp{showable} class
  to the values in such a list.

  @example
-:- func process_list(list_of_showable) = list(string).
+:- func process_list(showable_list) = list(string).
  process_list(nil) = "".
  process_list(cons(Head, Tail)) = [show(Head) | process_list(Tail)].
  @end example