Add Araxis Merge support for Mac OS/X

[talios]

Araxis Merge is available on OS/X via:

/Applications/Araxis Merge.app/Contents/Utilities/compare

as documented at https://www.araxis.com/merge/documentation-os-x/command-line.en

[LarsEckart]

hello and thank you for your contribution.

We'll take this in next Monday when we get together again. If you want to join, let me know your email address and I send you an invite :)