Request Double internal information from the CURL session

Property definitions

curl $ NativeCurl :: easy_getinfo_double
	# Request Double internal information from the CURL session
	fun easy_getinfo_double(opt: CURLInfoDouble): nullable Float
	do
		 var answ = new Ref[Float](0.0)
		 if not native_getinfo_double(opt, answ).is_ok then return null
		 return answ.item
	end
lib/curl/native_curl.nit:149,2--155,4