Add Xojo language support

Add support for Xojo language, formerly called REALbasic (which is already in `languages.yml`).

Some wild examples:

* https://github.com/Hawkcode/MemberTree
* https://github.com/oleman108/imSplitter
* https://github.com/Olivier61/Icare---GitHub
* https://github.com/paullefebvre/xojotest
* https://github.com/jcowgar/xojo-format-code
* https://github.com/LyricsMaster/COMProxy

The example script is taken from http://en.wikipedia.org/wiki/Xojo