for-each-ref, quote: convert *_quote_print -> *_quote_buf

for-each-ref, quote: convert *_quote_print -> *_quote_buf

The print_value() function in for-each-ref.c prints values to stdout
immediately using {sq|perl|python|tcl}_quote_print().  Change these
lower-level quote functions to instead leave their results in strbuf
so that we can later add post-processing to the results of them.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>