fix duplicate symbol issue

Former-commit-id: 3568d652f738cda9124116a44f7430e884e92cb6

include/igl/marching_cubes.cpp

@@ -27,9 +27,9 @@
 #include "marching_cubes_tables.h"
 #include <map>
 
-extern int edgeTable[256];
-extern int triTable[256][2][17];
-extern int polyTable[8][16];
+extern const int edgeTable[256];
+extern const int triTable[256][2][17];
+extern const int polyTable[8][16];
 
 class EdgeKey 
 {

include/igl/marching_cubes_tables.h

@@ -33,7 +33,7 @@
 //int triTable[256][2][17];
 //int polyTable[8][16];
 
-int edgeTable[256]=
+const int edgeTable[256]=
 {
   0x0  , 0x109, 0x203, 0x30a, 0x406, 0x50f, 0x605, 0x70c,
   0x80c, 0x905, 0xa0f, 0xb06, 0xc0a, 0xd03, 0xe09, 0xf00,
@@ -73,7 +73,7 @@ int edgeTable[256]=
 //-----------------------------------------------------------------------------
 
 
-int triTable[256][2][17] =
+const int triTable[256][2][17] =
 {{{-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1},
   { 0, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1}},
   
@@ -896,7 +896,7 @@ int triTable[256][2][17] =
 //-----------------------------------------------------------------------------
 
 
-int polyTable[8][16] =
+const int polyTable[8][16] =
 {
   {-1},
   {-1},