fix bug extruded volume:

The parser wanted to create extruded volume begining systematically from 1. 
Thus, when there already existed volumes with number 1,2,3,etc, extruded volumes was created.

Common/OpenFile.cpp

@@ -152,22 +152,6 @@ void AddToTemporaryBoundingBox(double x, double y, double z)
   for(int i = 0; i < 3; i++) CTX::instance()->cg[i] = temp_bb.center()[i];
 }
 
-static void ComputeMaxEntityNum()
-{
-  GModel::current()->getGEOInternals()->MaxPointNum =
-    std::max(GModel::current()->getGEOInternals()->MaxPointNum,
-             GModel::current()->getMaxElementaryNumber(0));
-  GModel::current()->getGEOInternals()->MaxLineNum =
-    std::max(GModel::current()->getGEOInternals()->MaxLineNum,
-             GModel::current()->getMaxElementaryNumber(1));
-  GModel::current()->getGEOInternals()->MaxSurfaceNum =
-    std::max(GModel::current()->getGEOInternals()->MaxSurfaceNum,
-             GModel::current()->getMaxElementaryNumber(2));
-  GModel::current()->getGEOInternals()->MaxVolumeNum =
-    std::max(GModel::current()->getGEOInternals()->MaxVolumeNum,
-             GModel::current()->getMaxElementaryNumber(3));
-}
-
 static std::vector<gmshFILE> openedFiles;
 
 int ParseFile(const std::string &fileName, bool close, bool warnIfMissing)
@@ -484,7 +468,7 @@ int MergeFile(const std::string &fileName, bool warnIfMissing, bool setWindowTit
     }
   }
 
-  ComputeMaxEntityNum();
+  GModel::current()->getGEOInternals()->ComputeMaxEntityNum();
   if(setBoundingBox) SetBoundingBox();
   CTX::instance()->geom.draw = 1;
   CTX::instance()->mesh.changed = ENT_ALL;

Geo/Geo.cpp

@@ -4544,6 +4544,7 @@ void GEO_Internals::alloc_all()
 {
   MaxPointNum = MaxLineNum = MaxLineLoopNum = MaxSurfaceNum = 0;
   MaxSurfaceLoopNum = MaxVolumeNum = MaxPhysicalNum = 0;
+  ComputeMaxEntityNum();
   Points = Tree_Create(sizeof(Vertex *), compareVertex);
   Curves = Tree_Create(sizeof(Curve *), compareCurve);
   EdgeLoops = Tree_Create(sizeof(EdgeLoop *), compareEdgeLoop);
@@ -4574,6 +4575,18 @@ void GEO_Internals::reset_physicals()
   List_Reset(PhysicalGroups);
 }
 
+void GEO_Internals::ComputeMaxEntityNum()
+{
+  MaxPointNum =
+    std::max(MaxPointNum, GModel::current()->getMaxElementaryNumber(0));
+  MaxLineNum =
+    std::max(MaxLineNum, GModel::current()->getMaxElementaryNumber(1));
+  MaxSurfaceNum =
+    std::max(MaxSurfaceNum, GModel::current()->getMaxElementaryNumber(2));
+  MaxVolumeNum =
+    std::max(MaxVolumeNum, GModel::current()->getMaxElementaryNumber(3));
+}
+
 int select_contour(int type, int num, List_T * List)
 {
   int k = 0;

Geo/Geo.h

@@ -297,6 +297,8 @@ class GEO_Internals{
   void reset_physicals();
   std::map<int,int> periodicFaces;
   std::map<int,int> periodicEdges;
+
+  void ComputeMaxEntityNum();
 };
 
 class Shape{