Coverity fixes: uncaught exceptions

src/tests/base64.cc

@@ -135,7 +135,11 @@ int main( int argc, char *argv[] )
     verbose = true;
   }
 
+  try {
     test_base64();
-
+  } catch ( const std::exception &e ) {
+    fprintf( stderr, "Error: %s\r\n", e.what() );
+    return 1;
+  }
   return 0;
 }

src/tests/ocb-aes.cc

@@ -544,8 +544,12 @@ int main( int argc, char *argv[] )
     verbose = true;
   }
 
+  try {
     test_all_vectors();
     test_iterative();
-
+  } catch ( const std::exception &e ) {
+    fprintf( stderr, "Error: %s\r\n", e.what() );
+    return 1;
+  }
   return 0;
 }