Helper method to add entire list of pairs to mail content

Property definitions

curl $ CurlMail :: add_pairs_to_content
	# Helper method to add entire list of pairs to mail content
	private fun add_pairs_to_content(content: String, pairs: HeaderMap): String
	do
		for h_key, h_val in pairs do content = add_pair_to_content(content, h_key, h_val)
		return content
	end
lib/curl/curl.nit:405,2--410,4