[specialized.algorithms.general] Restore the note

... for potentially-overlapping objects and undefined behavior.

The original note was incorrect and removed. But it turns out that
_some_ note is still helpful. This PR tries to find the right way to
describe storage reusing and potential subsequent undefined behavior.

Co-authored-by: Jonathan Wakely <[email protected]>

source/algorithms.tex

@@ -11156,6 +11156,16 @@
 are destroyed in an unspecified order
 before allowing the exception to propagate.
 
+\pnum
+\begin{note}
+When new objects are created by
+the algorithms specified in \ref{specialized.algorithms},
+the lifetime ends for any existing objects
+(including potentially-overlapping subobjects \ref{intro.object})
+in storage that is reused \ref{basic.life}.
+Subsequent operations on these objects can result in undefined behavior.
+\end{note}
+
 \pnum
 Some algorithms specified in \ref{specialized.algorithms}
 make use of the exposition-only function template