[optional.monaic] Restore wording effected by LWG3973.

Both LWG3973 (Motion 1) and P2407R5 (Motion 3) modified this wording:
LWG3973 changes "value()" to "*val" to address ADL concerns, and
P2407R5 changed "value()" to "**this" to be freestanding. In light of
the former, the latter should also use "*val".

Independently, additional problems have been discovered with LWG3973,
but those will be addressed by a future LWG issue.

Author: tkoeppe

source/utilities.tex

@@ -4172,7 +4172,7 @@
 Equivalent to:
 \begin{codeblock}
 if (*this) {
-  return invoke(std::forward<F>(f), **this);
+  return invoke(std::forward<F>(f), *val);
 } else {
   return remove_cvref_t<U>();
 }
@@ -4187,7 +4187,7 @@
 
 \begin{itemdescr}
 \pnum
-Let \tcode{U} be \tcode{invoke_result_t<F, decltype(std::move(**this))>}.
+Let \tcode{U} be \tcode{invoke_result_t<F, decltype(std::move(*val))>}.
 
 \pnum
 \mandates
@@ -4198,7 +4198,7 @@
 Equivalent to:
 \begin{codeblock}
 if (*this) {
-  return invoke(std::forward<F>(f), std::move(**this));
+  return invoke(std::forward<F>(f), std::move(*val));
 } else {
   return remove_cvref_t<U>();
 }
@@ -4213,15 +4213,15 @@
 
 \begin{itemdescr}
 \pnum
-Let \tcode{U} be \tcode{remove_cv_t<invoke_result_t<F, decltype(**this)>>}.
+Let \tcode{U} be \tcode{remove_cv_t<invoke_result_t<F, decltype(*val)>>}.
 
 \pnum
 \mandates
 \tcode{U} is a non-array object type
 other than \tcode{in_place_t} or \tcode{nullopt_t}.
 The declaration
 \begin{codeblock}
-U u(invoke(std::forward<F>(f), **this));
+U u(invoke(std::forward<F>(f), *val));
 \end{codeblock}
 is well-formed for some invented variable \tcode{u}.
 \begin{note}
@@ -4232,7 +4232,7 @@
 \returns
 If \tcode{*this} contains a value, an \tcode{optional<U>} object
 whose contained value is direct-non-list-initialized with
-\tcode{invoke(std::forward<F>(f), **this)};
+\tcode{invoke(std::forward<F>(f), *val)};
 otherwise, \tcode{optional<U>()}.
 \end{itemdescr}
 
@@ -4245,15 +4245,15 @@
 \begin{itemdescr}
 \pnum
 Let \tcode{U} be
-\tcode{remove_cv_t<invoke_result_t<F, decltype(std::move(**this))>>}.
+\tcode{remove_cv_t<invoke_result_t<F, decltype(std::move(*val))>>}.
 
 \pnum
 \mandates
 \tcode{U} is a non-array object type
 other than \tcode{in_place_t} or \tcode{nullopt_t}.
 The declaration
 \begin{codeblock}
-U u(invoke(std::forward<F>(f), std::move(**this)));
+U u(invoke(std::forward<F>(f), std::move(*val)));
 \end{codeblock}
 is well-formed for some invented variable \tcode{u}.
 \begin{note}
@@ -4264,7 +4264,7 @@
 \returns
 If \tcode{*this} contains a value, an \tcode{optional<U>} object
 whose contained value is direct-non-list-initialized with
-\tcode{invoke(std::forward<F>(f), std::move(**this))};
+\tcode{invoke(std::forward<F>(f), std::move(*val))};
 otherwise, \tcode{optional<U>()}.
 \end{itemdescr}