Get a list of the keys associated to key

Property definitions

curl $ HeaderMap :: []
	# Get a list of the keys associated to `key`
	fun [](k: String): Array[String]
	do
		var res = new Array[String]
		for c in array do if c.first == k then res.add c.second
		return res
	end
lib/curl/curl.nit:614,2--620,4