feat(gencat): add gencat implementation for GNU and OSX

[rishadbaniya]

the tests file contain *.cat file (which are the binary catalog file generated by gencat tool available in respective platform i.e OSX and the one that uses GNU)

So we are testing our result against output in those two platforms.

FYI: POSIX specification implies on the structure of the message file and not the binary catalog file, so it seems throughout time both OSX(which copied most of its implementation from BSD) and any OS that uses GNU(let's say linux) have developed their own version of binary catalog file and they completely differ from each other as of now

So, to implement gencat, means to adhere by those binary catalog format for that specific platform(hence the source code is needed)..luckily got the source code for OSX and GNU implementation(which were open source)