Avoid ambiguous ctor call (uint32_t vs DB_ENV*) with db 6.x.

--- ice-3.6.3/cpp/src/Freeze/SharedDbEnv.cpp.orig	2016-10-05 16:59:08.000000000 +0200
+++ ice-3.6.3/cpp/src/Freeze/SharedDbEnv.cpp	2017-06-28 18:42:43.411869639 +0200
@@ -530,7 +530,7 @@
     {
         if(_env == 0)
         {
-            _envHolder.reset(new DbEnv(0));
+            _envHolder.reset(new DbEnv(0u));
             _env = _envHolder.get();
 
             if(_trace >= 1)
--- ice-3.6.3/cpp/src/FreezeScript/transformdb.cpp.orig	2016-10-05 16:59:08.000000000 +0200
+++ ice-3.6.3/cpp/src/FreezeScript/transformdb.cpp	2017-06-28 19:15:03.928514164 +0200
@@ -766,8 +766,8 @@
     //
     // Transform the database.
     //
-    DbEnv dbEnv(0);
-    DbEnv dbEnvNew(0);
+    DbEnv dbEnv(0u);
+    DbEnv dbEnvNew(0u);
     Freeze::TransactionPtr txNew;
     Freeze::ConnectionPtr connection;
     Freeze::ConnectionPtr connectionNew;
--- ice-3.6.3/cpp/src/FreezeScript/Util.cpp.orig	2016-10-05 16:59:08.000000000 +0200
+++ ice-3.6.3/cpp/src/FreezeScript/Util.cpp	2017-06-28 19:22:29.318509063 +0200
@@ -209,7 +209,7 @@
 {
     CatalogDataMap result;
 
-    DbEnv dbEnv(0);
+    DbEnv dbEnv(0u);
     try
     {
 #ifdef _WIN32
--- ice-3.6.3/cpp/src/FreezeScript/DumpDB.cpp.orig	2016-10-05 16:59:08.000000000 +0200
+++ ice-3.6.3/cpp/src/FreezeScript/DumpDB.cpp	2017-06-28 19:33:38.555168088 +0200
@@ -481,7 +481,7 @@
     FreezeScript::ObjectFactoryPtr objectFactory = new FreezeScript::ObjectFactory;
     communicator->addObjectFactory(objectFactory, "");
 
-    DbEnv dbEnv(0);
+    DbEnv dbEnv(0u);
     DbTxn* txn = 0;
     Freeze::ConnectionPtr connection;
     int status = EXIT_SUCCESS;