EOS support on MacOS X

Thanks to a gratuitous donation of an iMac computer by Prof. Leo van Hemmen, we can now actively support building and using EOS on Mac OS X. We thank Professor van Hemmen very much for his donation!

The test hardware in use is limited to Mac OS 10.11 (El Capitan). We would be happy to receive reports about EOS builds on more recent Mac OS versions. The installation on MacOS via the Homebrew package manager is documented in the manual. The minimal commands necessary to build the most recent development version are

brew tap eos/eos
brew install --HEAD eos