save onWhat() as vertex tag in .mesh format

Fltk/menuWindow.cpp

@@ -2511,7 +2511,7 @@ contextItem menu_mesh[] = {
     {"1Mesh>Define"} ,
     {"Fields",      (Fl_Callback *)field_cb},
     {"Characteristic length", (Fl_Callback *)mesh_define_length_cb  } ,
-    {"Embedded point", (Fl_Callback *)mesh_define_embedded_cb, (void*)"point" } ,
+    {"Embedded points", (Fl_Callback *)mesh_define_embedded_cb, (void*)"point" } ,
     {"Recombine",   (Fl_Callback *)mesh_define_recombine_cb  } ,
     {"Transfinite", (Fl_Callback *)mesh_define_transfinite_cb  } , 
     {""} 

Geo/MVertex.cpp

@@ -154,7 +154,8 @@ void MVertex::writeMESH(FILE *fp, double scalingFactor)
   if(_index < 0) return; // negative index vertices are never saved
 
   fprintf(fp, " %20.14G      %20.14G      %20.14G      %d\n", 
-          x() * scalingFactor, y() * scalingFactor, z() * scalingFactor, _index);
+          x() * scalingFactor, y() * scalingFactor, z() * scalingFactor, 
+          _ge ? _ge->tag() : 0);
 }
 
 static void double_to_char8(double val, char *str)