Amend documentation for text-quoting-style becoming a user option.

Amend documentation for text-quoting-style becoming a user option.

* doc/lispref/control.texi (Signaling Errors):
* doc/lispref/display.texi (Displaying Messages):
* doc/lispref/strings.texi (Formatting Strings):
Edit for brevity, farming out the details to the new
Text Quoting Style node.
* doc/lispref/help.texi (Text Quoting Style): New section.
Move detailed discussion of text-quoting-style here.
Add discussion about how to output grave accent and apostrophe in
documentation and messages.  Adjust xrefs to point to this section
when appropriate.
* etc/NEWS: text-quoting-style semantics have not changed.