Proper rounding of displayed and spoken values

This is something that has bugged me. My main bugger was A2 battery voltage, that I scale to show a voltage of one lipo cell. In this instance values spoken with one decimal place are only useful if there is proper rounding of hundredths. So for example A2 value of 3.79 volts was previously spoken as 3.7V, after this correction is spoken as 3.8V.

Then I expanded this mechanism to all other values that are scaled down. Somebody should check, but I probably missed some values. Please add rounding to any such value.

There was also a bug in English tts: be5e6f678afeb9a4e5c1af8e3e3277eae9266073

The new function name div10_and_round() is something I am not proud of, but I couldn't think on anything better.