PR# 19680 WEL_DIB

I have amended 'destroy_item' in class WEL_DIB to the following as I have a suspicion that an SDL surface pixel pointer was being held onto when a DIB object was created in one of my routines when using 'make_with_info_and_data'.  I have a wrapper for Simple Direct Medialayer that I am using that led me to this suspicion as I was having some issues.

destroy_item
			-- Free all GDI resource allocated by Current
		do
			if palette.reference_tracked then
				palette.decrement_reference
			elseif palette.references_count = 0 then
				palette.delete
			end
			info_header.dispose
			Precursor
		end