* If this param is set to 0, the previous behavior is used.
* Else the solder mask is plotted as polygon, with shapes near than  this min width value are  merged.
Pcbnew in nanometer version: fix a serious rounding issue due to the fact dialogs were using 4 digits for mantissa.
* This is not enough for nanometer coordinates ( 8 are needed to display a value in inches),
*  so sometimes after closing a dialog, some coordinates were modified, although no new value was entered.
Minor other bug fixed.