close[t:3880] Fix the cxx compile. Refs #3880.

git-svn-id: file:///svn/toku/tokudb@34017 c7de825b-a66e-492c-adef-691d508d4ae1

cxx/dbenv.cpp

 #include <stdarg.h>
-#include <assert.h>
 #include <errno.h>
+#include <toku_assert.h>
 #include "../newbrt/brttypes.h"
 #include <db_cxx.h>