Support building on MaxOS X

[ensonic]

Let do a few more rounds of attaching gist, fixing the issues and updating the [docs](http://wiki.buzztrax.org/index.php/Building#MacOSX docs).

[andredublin]

Terminal output errors for reference.
https://gist.github.com/andredublin/82e398eb20ec8414b74c

[ensonic]

@andredublin , for the bootstrapping the build you'd need "gettext" and "gtk-doc". Regarding the gettext one this could need "In order for autopoint to be found you need to export PATH=${PATH}:/usr/local/opt/gettext/bin." as mentioned on the wiki (see the docs link in comment 1.