Fix spurious before-change-functions invocation from (insert ?\n).

Fix spurious before-change-functions invocation from (insert ?\n).
textprop.c (set_text_properties): rename parameter
`signal_after_change_p' to `coherent_change_p', and make the invocation
of `modify_region' conditional on it.

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modified:
  src/ChangeLog
  src/textprop.c
unknown:
  Makefile
  config.log
  config.status
  doc/emacs/Makefile
  doc/lispintro/Makefile
  doc/lispref/Makefile
  doc/misc/Makefile
  etc/DOC-23.1.91.1
  leim/Makefile
  leim/changed.misc
  leim/changed.tit
  lib-src/Makefile
  lib-src/Makefile.c
  lib-src/b2m
  lib-src/ctags
  lib-src/digest-doc
  lib-src/ebrowse
  lib-src/emacsclient
  lib-src/etags
  lib-src/fakemail
  lib-src/hexl
  lib-src/make-docfile
  lib-src/movemail
  lib-src/profile
  lib-src/sorted-doc
  lib-src/test-distrib
  lib-src/update-game-score
  lisp/Makefile
  lwlib/Makefile
  oldXMenu/Makefile
  src/Makefile
  src/Makefile.c
  src/bootstrap-emacs
  src/deps/
  src/emacs
  src/emacs-23.1.91.1
  src/prefix-args
  src/stamp-oldxmenu
  src/temacs