CWG2654 Un-deprecation of compound volatile assignments

Fixes NB US 045 (C++23 CD).

Author: burblebee

source/expressions.tex

@@ -7191,10 +7191,9 @@
 The behavior of an expression of the form \tcode{E1 \placeholder{op}= E2}
 is equivalent to \tcode{E1 = E1 \placeholder{op} E2} except
 that \tcode{E1} is evaluated only once.
-Such expressions are deprecated
-if \tcode{E1} has volatile-qualified type
-and \placeholder{op} is not one of the bitwise operators
-\tcode{|}, \tcode{\&}, \tcode{\caret}; see~\ref{depr.volatile.type}.
+\begin{note}
+The object designated by \tcode{E1} is accessed twice.
+\end{note}
 For \tcode{+=} and \tcode{-=},
 \tcode{E1} shall either have arithmetic type or be a pointer to a
 possibly cv-qualified completely-defined object type. In all other

source/future.tex

@@ -104,9 +104,7 @@
 brachiosaur = neck;                 // OK
 tail = brachiosaur;                 // OK
 tail = brachiosaur = neck;          // deprecated
-brachiosaur += neck;                // deprecated
-brachiosaur = brachiosaur + neck;   // OK
-brachiosaur |= neck;                // OK, bitwise compound expression
+brachiosaur += neck;                // OK
 \end{codeblock}
 \end{example}