[vlc-devel] Sorting by disc number

[Wieland Hoffmann]

Hi,

the following two patches allow sorting items in the media library and
playlist by disc number, in addition to the existing methods. This is
especially useful by combining it with sorting by track number because
then you'll actually get sensible results for music from multi-disc
releases. Unfortunately there doesn't seem to be any option to always
sort based on multiple columns, so the sorting requires multiple steps
to be useful.

The first patch implements that, the second one just changes the english
string for vlc_meta_DiscNumber to "Disc number" (mimicking the one for
vlc_meta_TrackNumber) because "DiscNumber" doesn't look too great when
used as a column name in the UI.