Merge 2024-03 LWG Motion 5

P2872R3 Remove wstring_convert From C++26

Author: tkoeppe

source/compatibility.tex

@@ -221,6 +221,18 @@
 \item \tcode{strstreambuf}
 \end{itemize}
 
+\nodiffref
+\change
+Remove convenience interfaces \tcode{wstring_convert} and
+\tcode{wbuffer_convert}.
+\rationale
+These features were underspecified with no clear error reporting mechanism and
+were deprecated for the last three editions of this standard.
+Ongoing support is at implementer's discretion,
+exercising freedoms granted by \ref{zombie.names}.
+\effect
+A valid \CppXXIII{} program using these interfaces may become ill-formed.
+
 \rSec1[diff.cpp20]{\Cpp{} and ISO \CppXX{}}
 
 \rSec2[diff.cpp20.general]{General}