Maine healthcare providers have unveiled a new information-sharing system that will eventually give doctors instant access to patients' medical histories no matter where they are located around the state. HealthInfoNet, or HIN, will allow doctors to call up a complete medical history report for patients that display recent diagnoses, lab test results and prescribed medications even when the work was done by physicians hundreds of miles away. More than $4 million has been raised so far to fund development of the online network.