Remove escape backslash from string

Property definitions

markdown2 :: markdown_inline_parsing $ String :: unescape_string
	# Remove escape backslash from string
	fun unescape_string: String do
		if not has(re_escaped) then return self

		var buffer = new Buffer
		var match = search(re_escaped)
		var last_end = 0
		while match != null do
			buffer.append substring(last_end, match.from - last_end)
			buffer.append substring(match.from + 1, 1)
			last_end = match.after
			match = search_from(re_escaped, last_end)
		end
		if last_end < length then
			buffer.append substring(last_end, length - last_end)
		end
		return buffer.to_s
	end
lib/markdown2/markdown_inline_parsing.nit:1370,2--1387,4