1) Add 32 Cu Layers.

2) Change from legacy Cu stack to counting down from top=(F_Cu or 0).
   The old Cu stack required knowing the count of Cu layers to make
   sense of the layer number when converting to many exported file types.
   The new Cu stack is more commonly used, although ours still gives
   B_Cu a fixed number.
3) Introduce class LSET and enum LAYER_ID.
4) Change *.kicad_pcb file format version to 4 from 3.
5) Change fixed names Inner1_Cu-Inner14_Cu to In1_Cu-In30_Cu and their
   meanings are typically flipped.
6) Moved the #define LAYER_N_* stuff into legacy_plugin.cpp where they
   can die a quiet death, and switch to enum LAYER_ID symbols throughout.
7) Removed the LEGACY_PLUGIN::Save() and FootprintSave() functions.
   You will need to convert to the format immediately, *.kicad_pcb and
   *.kicad_mod (=pretty) since legacy format was never going to know
   about 32 Cu layers and additional technical layers and the reversed Cu
   stack.

pcbnew/plot_brditems_plotter.cpp

@@ -57,7 +57,7 @@
 
 EDA_COLOR_T BRDITEMS_PLOTTER::getColor( LAYER_NUM aLayer )
 {
-    EDA_COLOR_T color = m_board->GetLayerColor( aLayer );
+    EDA_COLOR_T color = m_board->GetLayerColor( (LAYER_ID) aLayer );
     if (color == WHITE)
         color = LIGHTGRAY;
     return color;
@@ -110,10 +110,10 @@ bool BRDITEMS_PLOTTER::PlotAllTextsModule( MODULE* aModule )
     TEXTE_MODULE* textModule = &aModule->Reference();
     LAYER_NUM     textLayer = textModule->GetLayer();
 
-    if( textLayer >= NB_LAYERS )
+    if( textLayer >= LAYER_ID_COUNT )       // how will this ever be true?
         return false;
 
-    if( ( GetLayerMask( textLayer ) & m_layerMask ) == 0 )
+    if( !m_layerMask[textLayer] )
         trace_ref = false;
 
     if( !textModule->IsVisible() && !GetPlotInvisibleText() )
@@ -122,10 +122,10 @@ bool BRDITEMS_PLOTTER::PlotAllTextsModule( MODULE* aModule )
     textModule = &aModule->Value();
     textLayer = textModule->GetLayer();
 
-    if( textLayer > NB_LAYERS )
+    if( textLayer > LAYER_ID_COUNT )        // how will this ever be true?
         return false;
 
-    if( ( GetLayerMask( textLayer ) & m_layerMask ) == 0 )
+    if( !m_layerMask[textLayer] )
         trace_val = false;
 
     if( !textModule->IsVisible() && !GetPlotInvisibleText() )
@@ -148,8 +148,7 @@ bool BRDITEMS_PLOTTER::PlotAllTextsModule( MODULE* aModule )
             PlotTextModule( &aModule->Value(), GetValueColor() );
     }
 
-    for( BOARD_ITEM *item = aModule->GraphicalItems().GetFirst();
-         item != NULL; item = item->Next() )
+    for( BOARD_ITEM *item = aModule->GraphicalItems().GetFirst(); item; item = item->Next() )
     {
         textModule = dyn_cast<TEXTE_MODULE*>( item );
 
@@ -161,10 +160,10 @@ bool BRDITEMS_PLOTTER::PlotAllTextsModule( MODULE* aModule )
 
         textLayer = textModule->GetLayer();
 
-        if( textLayer >= NB_LAYERS )
+        if( textLayer >= LAYER_ID_COUNT )
             return false;
 
-        if( !( GetLayerMask( textLayer ) & m_layerMask ) )
+        if( !m_layerMask[textLayer] )
             continue;
 
         PlotTextModule( textModule, getColor( textLayer ) );
@@ -246,7 +245,7 @@ void BRDITEMS_PLOTTER::PlotTextModule( TEXTE_MODULE* pt_texte, EDA_COLOR_T aColo
 
 void BRDITEMS_PLOTTER::PlotDimension( DIMENSION* aDim )
 {
-    if( (GetLayerMask( aDim->GetLayer() ) & m_layerMask) == 0 )
+    if( !m_layerMask[aDim->GetLayer()] )
         return;
 
     DRAWSEGMENT draw;
@@ -255,6 +254,7 @@ void BRDITEMS_PLOTTER::PlotDimension( DIMENSION* aDim )
     draw.SetLayer( aDim->GetLayer() );
 
     EDA_COLOR_T color = aDim->GetBoard()->GetLayerColor( aDim->GetLayer() );
+
     // Set plot color (change WHITE to LIGHTGRAY because
     // the white items are not seen on a white paper or screen
     m_plotter->SetColor( color != WHITE ? color : LIGHTGRAY);
@@ -295,7 +295,7 @@ void BRDITEMS_PLOTTER::PlotPcbTarget( PCB_TARGET* aMire )
 {
     int     dx1, dx2, dy1, dy2, radius;
 
-    if( (GetLayerMask( aMire->GetLayer() ) & m_layerMask) == 0 )
+    if( !m_layerMask[aMire->GetLayer()] )
         return;
 
     m_plotter->SetColor( getColor( aMire->GetLayer() ) );
@@ -353,7 +353,7 @@ void BRDITEMS_PLOTTER::Plot_Edges_Modules()
         {
             EDGE_MODULE* edge = dyn_cast<EDGE_MODULE*>( item );
 
-            if( !edge || (( GetLayerMask( edge->GetLayer() ) & m_layerMask ) == 0) )
+            if( !edge || !m_layerMask[edge->GetLayer()] )
                 continue;
 
             Plot_1_EdgeModule( edge );
@@ -447,7 +447,7 @@ void BRDITEMS_PLOTTER::PlotTextePcb( TEXTE_PCB* pt_texte )
     if( pt_texte->GetText().IsEmpty() )
         return;
 
-    if( ( GetLayerMask( pt_texte->GetLayer() ) & m_layerMask ) == 0 )
+    if( !m_layerMask[pt_texte->GetLayer()] )
         return;
 
     m_plotter->SetColor( getColor( pt_texte->GetLayer() ) );
@@ -575,13 +575,13 @@ void BRDITEMS_PLOTTER::PlotFilledAreas( ZONE_CONTAINER* aZone )
 
 /* Plot items type DRAWSEGMENT on layers allowed by aLayerMask
  */
-void BRDITEMS_PLOTTER::PlotDrawSegment(  DRAWSEGMENT* aSeg )
+void BRDITEMS_PLOTTER::PlotDrawSegment( DRAWSEGMENT* aSeg )
 {
     int     thickness;
     int     radius = 0;
     double  StAngle = 0, EndAngle = 0;
 
-    if( (GetLayerMask( aSeg->GetLayer() ) & m_layerMask) == 0 )
+    if( !m_layerMask[aSeg->GetLayer()] )
         return;
 
     if( GetMode() == LINE )