Allow `text-quoting-style' to be `leave', i.e. no translation of quotes.

Allow `text-quoting-style' to be `leave', i.e. no translation of quotes.

* lisp/help-fns.el (describe-function-1): Don't set coding system to UTF-8
when text-quoting-style is `leave'.

* src/lisp.h (enum text_quoting_style): Add identifier LEAVE_QUOTING_STYLE.

* src/doc.c (syms_of_doc): New symbol "leave".  Amend doc string of
`text_quoting_style'.
(text_quoting_style): Handle `leave' by returning LEAVE_QUOTING_STYLE.
(Fsubstitute_command_keys): Don't translate quotes when quoting_style is
LEAVE_QUOTING_STYLE.

* src/editfns.c (styled_format): Set quoting_style to -1 when
text-quoting-style is `leave'.