The mint function transfers an asset into the protocol, which begins accumulating interest based on the current Supply Rate for the asset. The user receives a quantity of aTokens equal to the underlying tokens supplied, divided by the current Exchange Rate.
function mint(uint mintAmount) returns (uint)
msg.sender: The account which shall supply the asset, and own the minted aTokens.
mintAmount: The amount of the asset to be supplied, in units of the underlying asset.