Make private quote_path() in wt-status.c available as quote_path_relative()

Make private quote_path() in wt-status.c available as quote_path_relative()

Move quote_path() from wt-status.c to quote.c and rename it as
quote_path_relative(), because it is a better name for a public function.

Also, instead of handcrafted quoting, quote_c_style_counted() is now used,
to make its quoting more consistent with the rest of the system, also
honoring core.quotepath specified in configuration.

Signed-off-by: Dmitry Potapov <dpotapov@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>