tdf#91195: vcl: reduce MapMode Fraction precision to avoid...

... overlow in ImplMapLogicToPixel.  50 bits is still too much, 44
appears to work for exporting PNG.

DocumentToGraphicRenderer::renderToGraphic() converts a double to
Fraction which is the source of the excess precision.

Change-Id: I93b11ef3a8be1c2f816f9697e5cd33eb00f7c2f9

vcl/source/gdi/mapmod.cxx

@@ -193,6 +193,7 @@ void MapMode::SetScaleX( const Fraction& rScaleX )
 
     ImplMakeUnique();
     mpImplMapMode->maScaleX = rScaleX;
+    mpImplMapMode->maScaleX.ReduceInaccurate(44);
 }
 
 void MapMode::SetScaleY( const Fraction& rScaleY )
@@ -200,6 +201,7 @@ void MapMode::SetScaleY( const Fraction& rScaleY )
 
     ImplMakeUnique();
     mpImplMapMode->maScaleY = rScaleY;
+    mpImplMapMode->maScaleY.ReduceInaccurate(44);
 }
 
 MapMode& MapMode::operator=( const MapMode& rMapMode )

vcl/source/outdev/map.cxx

@@ -78,6 +78,7 @@ static Fraction ImplMakeFraction( long nN1, long nN2, long nD1, long nD2 )
         aF = Fraction( i*nN1, nD1 ) * Fraction( nN2, nD2 );
     }
 
+    aF.ReduceInaccurate(44);
     return aF;
 }