Ignores any character until a JSON separator is encountered

Property definitions

json $ JSONStringParser :: ignore_until_separator
	# Ignores any character until a JSON separator is encountered
	fun ignore_until_separator do
		var max = len
		while pos < max do
			if not src[pos].is_json_separator then return
		end
	end
lib/json/static.nit:449,2--455,4