bisect--helper: reimplement `bisect_log` shell function in C

bisect--helper: reimplement `bisect_log` shell function in C

Reimplement the `bisect_log()` shell function in C and also add
`--bisect-log` subcommand to `git bisect--helper` to call it from
git-bisect.sh .

Using `--bisect-log` subcommand is a temporary measure to port shell
function to C so as to use the existing test suite.

Mentored-by: Lars Schneider <larsxschneider@gmail.com>
Mentored-by: Christian Couder <chriscool@tuxfamily.org>
Mentored-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Helped-by: Rafael Silva <rafaeloliveira.cs@gmail.com>
Signed-off-by: Pranit Bauva <pranit.bauva@gmail.com>
Signed-off-by: Tanushree Tumane <tanushreetumane@gmail.com>
Signed-off-by: Miriam Rubio <mirucam@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>