[lex.charset] Rebase onto main

Also, merge the sentence on where universal characters
are prohibited into the sentence describing universal
characters, to make clear that there is no contradiction
between nominating a character, and how that character
can be used.

source/lex.tex

@@ -430,8 +430,20 @@
 \end{bnf}
 
 \pnum
-The \grammarterm{universal-character-name} construct provides a way to name
-any element in the translation character set using just the basic character set.
+The \grammarterm{universal-character-name} construct provides a way to name any
+element in the translation character set using just the basic character set.
+If a \grammarterm{universal-character-name} outside
+the \grammarterm{c-char-sequence}, \grammarterm{s-char-sequence}, or
+\grammarterm{r-char-sequence} of a \grammarterm{character-literal} or
+\grammarterm{string-literal}
+(in either case, including within a \grammarterm{user-defined-literal})
+corresponds to a control character or to a character in the basic character set,
+the program is ill-formed.
+\begin{note}
+A sequence of characters resembling a \grammarterm{universal-character-name} in an
+\grammarterm{r-char-sequence}\iref{lex.string} does not form a
+\grammarterm{universal-character-name}.
+\end{note}
 
 \pnum
 A \grammarterm{universal-character-name}
@@ -460,20 +472,6 @@
 None of these names or aliases have leading or trailing spaces.
 \end{note}
 
-\pnum
-If a \grammarterm{universal-character-name} outside
-the \grammarterm{c-char-sequence}, \grammarterm{s-char-sequence}, or
-\grammarterm{r-char-sequence} of
-a \grammarterm{character-literal} or \grammarterm{string-literal}
-(in either case, including within a \grammarterm{user-defined-literal})
-corresponds to a control character or
-to a character in the basic character set, the program is ill-formed.
-\begin{note}
-A sequence of characters resembling a \grammarterm{universal-character-name} in an
-\grammarterm{r-char-sequence}\iref{lex.string} does not form a
-\grammarterm{universal-character-name}.
-\end{note}
-
 \rSec1[lex.comment]{Comments}
 
 \pnum