[bigint/zxing-cpp] Adapter xcode 5.1.1 and set it as a dependency of zxing-cpp

[JackBoosY]

#12532 pipeline test reported error:

/Volumes/data/installed/x64-osx/include/bigint/BigUnsigned.hh:23:24: error: ISO C++11 does not allow access declarations; use using declarations instead
        NumberlikeArray<Blk>::N;
                              ^
        using 
/Volumes/data/installed/x64-osx/include/bigint/BigUnsigned.hh:87:24: error: ISO C++11 does not allow access declarations; use using declarations instead
        NumberlikeArray<Blk>::getCapacity;
                              ^
        using 
/Volumes/data/installed/x64-osx/include/bigint/BigUnsigned.hh:88:24: error: ISO C++11 does not allow access declarations; use using declarations instead
        NumberlikeArray<Blk>::getLength;
                              ^
        using 
3 errors generated.

This is because port zxing-cpp uses the built-in source bigint, and because port bigint is built before port zxing-cpp, resulting in port zxing-cpp using port bigint header files.
So I use the modification of zxing-cpp to adapt bigint to xcode 5.1.1.

[PhoebeHui]

LGTM