Avoid backslash-newline-newline in source code

* etc/refcards/Makefile (PDF_FRENCH):
* lib-src/etags.c (LOOP_ON_INPUT_LINES):
* lisp/dabbrev.el (dabbrev-check-other-buffers):
* lisp/org/org-id.el (org-id-link-to-org-use-id):
* lisp/org/org.el (org-support-shift-select, org-file-apps):
* src/alloc.c (CHECK_ALLOCATED_AND_LIVE)
(CHECK_ALLOCATED_AND_LIVE_SYMBOL):
* src/frame.h (FRAME_PIXEL_WIDTH_TO_TEXT_COLS):
* src/regex-emacs.c (PREFETCH_NOLIMIT):
* src/window.h (WINDOW_BUFFER):
Remove backslash-newline that immediately precedes another
newline, as this is not the usual style and is confusing.
1 job for master in 51 minutes and 5 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
failed #1889
test-all

00:51:05

 
Name Stage Failure
failed
test-all Test
Makefile:318: recipe for target 'check-doit' failed
make[2]: *** [check-doit] Error 1
make[2]: Leaving directory '/builds/emacs/emacs/test'
Makefile:293: recipe for target 'check-expensive' failed
make[1]: *** [check-expensive] Error 2
make[1]: Leaving directory '/builds/emacs/emacs/test'
Makefile:957: recipe for target 'check-expensive' failed
make: *** [check-expensive] Error 2
ERROR: Job failed: exit code 1