Fix a collision with a Windows define and our use of the same var name.

We use IN for INCH as units, but IN is defined in a Windows header

(cherry picked from commit b0fe4df3c5)
(cherry picked from commit 0acdabd1eb)
(cherry picked from commit eaa1e6d594)

common/plotters/DXF_plotter.cpp

@@ -141,7 +141,7 @@ void DXF_PLOTTER::SetUnits( DXF_UNITS aUnit )
         m_measurementDirective = 1;
         break;
 
-    case DXF_UNITS::IN:
+    case DXF_UNITS::INCH:
     default:
         m_unitScalingFactor = 0.0001;
         m_measurementDirective = 0;