Make text-quoting-style customizable. Introduce t and new meaning for nil.

A value of nil for text-quoting-style now means "no translation".  t means
"Use curved quotes if displayable".

* src/doc.c (text-quoting-style (function)): modify for new semantics.
(text-quoting-style (variable)): Amend the doc string, set the default value
to t.

* lisp/cus-start.el: (top level): Create a customize entry for
text-quoting-style in group display.

* etc/NEWS: Amend the entry for text-quoting-style.

* doc/emacs/display.texi (Text Display): Describe the translation of ASCII
quotes to curved quotes, and how to influence or inhibit it.

* doc/lispref/control.texi (Signalling Errors)
* doc/lispref/display.texi (Displaying Messages)
* doc/lispref/strings.texi (Formatting Strings): Describe binding
text-quoting-style to nil to inhibit unwanted quote translation.

* doc/lispref/help.texi (Keys in Documentation): Change text-quoting-style
from a variable to a user option.  Describe its changed set of values.  State
that it can be customized freely.

1 files changed, 5 insertions, 2 deletions

diff --git a/doc/lispref/strings.texi b/doc/lispref/strings.texi
index 219225d412b..117a373a190 100644
--- a/doc/lispref/strings.texi
+++ b/doc/lispref/strings.texi
@@ -835,8 +835,11 @@ A format that quotes with grave accents and apostrophes @t{`like
 this'} typically generates curved quotes @t{‘like this’}.  In
 contrast, a format that quotes with only apostrophes @t{'like this'}
 typically generates two closing curved quotes @t{’like this’}, an
-unusual style in English.  @xref{Keys in Documentation}, for how the
-@code{text-quoting-style} variable affects generated quotes.
+unusual style in English.  One way around such problems is to bind
+@code{text-quoting-style} to @code{nil} around calls to
+@code{format-message}; this causes the @acronym{ASCII} quoting
+characters to be output unchanged.  @xref{Keys in Documentation}, for
+how the @code{text-quoting-style} variable affects generated quotes.
 @end defun
 
 @cindex @samp{%} in format