Associations created only at install time

Currently file associations are created at install time in this nsis script.

Unfortunately this means that if user deselects any association at install time, appropriate keys for HKCR\VLC.$ext and HKLM\Software\Clients\Media\VLC\Capabilities\FileAssociations will not be created thus changing associations at runtime through VLC preferences (which calls system applet) will not be possible (at least in WinVista/7).

Proposed change:

1. Always create HKCR\VLC.$ext and HKLM\Software\Clients\Media\VLC\Capabilities\FileAssociations for all extensions but only set HKCR\.$ext = VLC.$ext when selected.

AND

2. Do the same at runtime when user clicks Set Associations button in VLC preferences and such entries do not yet exist.

Also Vista detection is not very future proof (it will break when windows reaches NT version 7.0), it's probably better to check for existence of HKLM\Software\Clients\Media or check if first version component is >=6 but since NSIS language is crap this could get ugly.

Unfortunately I can't provide a patch :(