New firmware for the Swissmicros DM15L

[Helix]

I’ve successfully installed this firmware on my credit card size DM-15. I like a lot this idea!
It’s not only more precise, but also faster than the SwissMicros Firmware.

A few remarks though:

- What is the meaning of "ser" at the right of the display?

- The font is nice, except for the 3, because if lighting conditions are not optimal it can easily be confused with an 8. I know this is the font chosen by HP, but it’s an unfortunate decision in my opinion.
Casio, Sharp and TI have a very different 3, to avoid this confusion:
http://www.thimet.de/CalcCollection/Calc...602P-M.JPG
http://www.thimet.de/CalcCollection/Calc...500A-M.JPG
https://upload.wikimedia.org/wikipedia/c..._TI-74.jpg

For my HP 50g, I modified the 3 by removing one pixel in the central bar, and this makes a clear difference:


- Some important functions are missing, like f PREFIX or g MEM, but I suppose they are not yet implemented.

- There is a bug with arctan(1)