Simplify ‘delete-trailing-whitespace’ by not treating \n as whitespace

* lisp/simple.el (delete-trailing-whitespace): Set newline’s character
syntax to non-whitespace so that ‘\s-’ regular expression does not match
it.

This simplifies the loop slightly since a simple ‘\s-+$’ can be used and
as a consequence ‘line-beginning-position’ function does not need to be
called any longer.

Furthermore, when newline has whitespace syntax, ‘\s-$’ regular
expression ends up matching empty lins since ‘\s-’ matches newline
characetr of proceeding line.  This leads to needless loop iterations.

Since previous change to ‘delete-trailing-whitespace’ already introduced
‘with-syntax-table’, take advantage of it and also overwrite newline’s
character syntax.

1 files changed, 2 insertions, 1 deletions

diff --git a/test/lisp/simple-tests.el b/test/lisp/simple-tests.el
index 2722544446d..97b6c491629 100644
--- a/test/lisp/simple-tests.el
+++ b/test/lisp/simple-tests.el
@@ -235,7 +235,8 @@
       (insert " \f \n \f \f \n\nlast\n")
       (delete-trailing-whitespace)
       (should (string-equal (buffer-string) " \f\n \f \f\n\nlast\n"))
-      (should (equal ?\s (char-syntax ?\f))))))
+      (should (equal ?\s (char-syntax ?\f)))
+      (should (equal ?\s (char-syntax ?\n))))))
 
 
 ;;; auto-boundary tests