zxing-cpp: new package, replacing zxing

ZXing was hosted on Google Code, which is a closing. The current link
was already redirecting to the github repo.

But upstream is no longer supporting the cpp bindings, it's now a Java
library/application.

A fork has been created from the latest cpp source of the original
upstream. So this commit creates a new package, zxing-cpp, and adds
Config.in.legacy handling for the old zxing pakcage that is removed.

[Thomas:
  - add a patch that improves the CMakeLists.txt file to add
    installation rules. This allows to remove the manual installation
    logic from zxing-cpp.mk.
  - make libiconv a normal optional dependency. No need to involve
    BR2_ENABLE_LOCALE in the condition, since libiconv can only be
    enabled when !BR2_ENABLE_LOCALE.
  - bump to the latest upstream version.
  - add hash file.]

Signed-off-by: Maxime Hadjinlian <maxime.hadjinlian@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>