Fixes internal pin parsing error in ASAP7 liberty file.

This fix addresses an issue I saw with the ASAP7 liberty files and
ABC. ASAP7 lists internal pins in its liberty file which ABC's liberty
parser doesn't account for. This causes an assert to be triggered. This
fix simply adds interal pins to the ignore list.

src/map/scl/sclLiberty.c

@@ -955,6 +955,8 @@ int Scl_LibertyReadPinDirection( Scl_Tree_t * p, Scl_Item_t * pPin )
             return 0;
         if ( !strcmp(pToken, "output") )
             return 1;
+        if ( !strcmp(pToken, "internal") )
+            return 2;
         break;
     }
     return -1;
@@ -1525,7 +1527,7 @@ Vec_Str_t * Scl_LibertyReadSclStr( Scl_Tree_t * p, int fVerbose, int fVeryVerbos
             float CapOne, CapRise, CapFall;
             if ( Scl_LibertyReadPinFormula(p, pPin) != NULL ) // skip output pin
                 continue;
-            assert( Scl_LibertyReadPinDirection(p, pPin) == 0 );
+            assert( Scl_LibertyReadPinDirection(p, pPin) == 0 || Scl_LibertyReadPinDirection(p, pPin) == 2);
             pName = Scl_LibertyReadString(p, pPin->Head);
             Vec_PtrPush( vNameIns, Abc_UtilStrsav(pName) );
             Vec_StrPutS_( vOut, pName );
@@ -1546,6 +1548,8 @@ Vec_Str_t * Scl_LibertyReadSclStr( Scl_Tree_t * p, int fVerbose, int fVeryVerbos
         {
             if ( !Scl_LibertyReadPinFormula(p, pPin) ) // skip input pin
                 continue;
+            if (Scl_LibertyReadPinDirection(p, pPin) == 2) // skip internal pin
+                continue;
             assert( Scl_LibertyReadPinDirection(p, pPin) == 1 );
             pName = Scl_LibertyReadString(p, pPin->Head);
             Vec_StrPutS_( vOut, pName );