Plug memory leak in COMPACT_COUNT_DISTINCT's push down (#11)

I spotted what appears to be a memory leak in ValuesToCompactAgg (COMPACT_COUNT_DISTINCT's "push down" function). The code allocates a new `char*` of size `byteSize` but never deallocates it. The pointer is passed to `ValueFactory::getTempBinary(…)`, which copies the given data rather than taking ownership of the pointer.

src/ee/executors/aggregateexecutor.cpp

@@ -538,10 +538,10 @@ class ValuesToCompactAgg : public CompactCountDistinctAgg {
     {
         assert (type == VALUE_TYPE_VARBINARY);
         uint32_t byteSize =  roaring().getSizeInBytes();
-        char *serializedBytes = new char[byteSize];
+        std::unique_ptr<char[]> serializedBytes(new char[byteSize]);
 
-        roaring().write(serializedBytes);
-        return ValueFactory::getTempBinaryValue(serializedBytes, byteSize);
+        roaring().write(serializedBytes.get());
+        return ValueFactory::getTempBinaryValue(serializedBytes.get(), byteSize);
     }
 };