Merge 2021-06 CWG Motion 7

P2223R2 Trimming whitespaces before line splicing

Author: tkoeppe

source/lex.tex

@@ -86,17 +86,18 @@
 
 \item
 \indextext{line splicing}%
-Each instance of a backslash character (\textbackslash)
-immediately followed by a new-line character is deleted, splicing
+Each sequence of a backslash character (\textbackslash)
+immediately followed by
+zero or more whitespace characters other than new-line followed by
+a new-line character is deleted, splicing
 physical source lines to form logical source lines. Only the last
 backslash on any physical source line shall be eligible for being part
 of such a splice.
 Except for splices reverted in a raw string literal, if a splice results in
 a character sequence that matches the
 syntax of a \grammarterm{universal-character-name}, the behavior is
 undefined. A source file that is not empty and that does not end in a new-line
-character, or that ends in a new-line character immediately preceded by a
-backslash character before any such splicing takes place,
+character, or that ends in a splice,
 shall be processed as if an additional new-line character were appended
 to the file.