Simplifying text-quoting-style a bit

[Paul Eggert <eggert@cs.ucla.edu>]

In <http://bugs.gnu.org/23425#95> I propose what I hope is a minor 
change to how Emacs formats messages containing quotes. In draft Emacs 
25, if the variable text-quoting-style has the value ‘grave’ then a call 
like (message "‘foo’") with curved quotes outputs a string like "`foo'" 
with grave quotes. This translation from curved to grave style is a 
relic of a now-abandoned quoting design, is not used within Emacs and is 
unlikely to be used elsewhere, and means that grave quoting does not 
output text as-is as one might expect. My proposal is to turn this 
feature off, so that grave quoting outputs text as-is (assuming the text 
does not contain %).

I am mentioning this on emacs-devel to give a heads-up to any developers 
who might be affected by this proposal.