XL survivor armour additions.

Added XL versions of the survivor winter suit/boots/gloves/hood and survivor fire suit/boots/gloves/hood. The implementation of the pre-existing XL survivor equipment didn't seem to be consistent between the XL masks and the XL vanilla suit parts, so I've followed the conventions of the XL masks (i.e. no changes to encumbrance or protection, and the suffix "_xl" added to the IDs). 

Admittedly I've not followed the masks' conventions in the item descriptions, but that's mainly because I'm lazy and just adding in the word 'massive' like the rest of the XL stuff was a lot easier.

The weights and volumes I just kinda guesstimated, so they might be a little wonky, but I don't think the originals were set in a precise way?