Incorrect gas calculations for CALL* gas stipend

[Baltoli]

The gas calculator on the site for CALL* family opcodes is not correct; it subtracts the "gas stipend" cost from the total externally-observable cost of making the call. This means that the results of gas calculations for CALL* opcodes are 2300 lower than they should be (confirmed by testing against evmone).

I believe the fix should just be to delete this line from the call gas calculator; the stipend amount is only relevant when constructing the message to be sent to the callee account, not to the external gas calculations for the whole call.