GUI: Unify "Default" options text
|Reported by:||jvprat||Owned by:||sev-|
There are two versions of the text that appears in option combos to select the default:
"<default>" appears in the language, platform, graphics mode and render mode options
"Default" appears in the music driver and output rate options
The attached patch changes "Default" to "<default>" (I think it's better because it's easier to see it's a different kind of option).
Ticket imported from: #1742574. Ticket imported from: patches/807.