Clearing bClError flag in NumericEvaluator::parseOk() made the
expression look valid, even if the flag has been set for a previous
token. Now it is cleared before an expression is parsed and verified
after parser finishes.
Fixes: lp:1756995
* https://bugs.launchpad.net/kicad/+bug/1756995
If ',' is used as decimal separator by the current locale a '.' is also accepted.
Also add support for units "mi", "th" and "in" as described in the documentation of pcbnew.
Fixes: lp:1751315
* https://bugs.launchpad.net/kicad/+bug/1751315