New firmware for the Swissmicros DM15L

[jebedeo]

Hi Jean-Charles, I found a very silly bug that was making everything slow and less precise: the step size for the integration at the very first pass was wrong, so the main loop was struggling to converge since it had a factor of 2 to fight against. Thanks for pointing out that it didn't converge fast even for a constant function, that led me to find the bug!

I fixed it now, and boy it is fast!

The precision 'n' set by the user with FIX/SCI/ENG is used to stop the integration when the estimated error is < 10^-n, as in the HP15C.

I am using a Romberg integration (Romberg) of order 0, equivalent to a trapezoidal integration.

Cheers!