New handling for URI scheme handlers

[Bastien Nocera]

Heya,

This morning I implemented in GNOME use of the x-scheme-handler/*
mime-type for applications to register their interest in handling
particular URI schemes.

I posted about it in:
http://www.hadess.net/2010/10/new-control-center-and-you.html
And have a blocker bug for GNOME applications in:
https://bugzilla.gnome.org/show_bug.cgi?id=631433

The attached patch is changes to the shared-mime-info spec to mention
the use of x-scheme-handler/* mime-types.

Any comments?

Cheers