Support PHP Desktop on Linux / Ubuntu.

Porting tips were described in this topic:
https://groups.google.com/d/topic/phpdesktop/y76-TlXQXxQ/discussion

Porting to Linux should be easier now using CEF views. Maybe this can be accomplished without even touching GTK.

• https://bitbucket.org/chromiumembedded/cef/issues/1749/expose-the-views-aura-framework-as-an
• https://bitbucket.org/chromiumembedded/cef/src/master/include/views/

One of users reported that phpdesktop-chrome works fine on Linux using WINE emulator: http://en.wikipedia.org/wiki/Wine_(software)

Related Issue (Mac OS support): Issue #78.