bug#31231: Symbol search broken in NEWS and ChangeLogs

[Juri Linkov]

Symbol search ‘M-s _’ fails to find symbols in NEWS and ChangeLogs where
symbols are quoted by apostrophes whose syntax is word-constituent.

I see two solutions:

1. Modify syntax tables to redefine syntax of ‘'’ back to its default
   that is punctuation or to expression quote:

   (defvar change-log-mode-syntax-table
     (let ((st (make-syntax-table)))
       (modify-syntax-entry ?' "'   " st)
       st)
     "Syntax table used while in `change-log-mode'.")

This solution is not applicable to NEWS files where
text-mode syntax tables are inherited via outline-mode
whose syntax table can't be changed.

2. In these files replace apostrophes by “LEFT SINGLE QUOTATION MARK” and
   “RIGHT SINGLE QUOTATION MARK” like are used in Info and Help buffers.