Change type of enum entry from uint8 to uint64 (for passing travis-ci tests)

[asmyasnikov]

Hi!
I was change type of enum entry from uint8 to uint16. This need for my private dialect. For example I have entry like this

    <enum name="MY_DIALECT_PARAM">
      <entry value="2048" name="MY_DIALECT_PARAM_END">
        <description></description>
      </entry>
    </enum>

And for value="2048" go-mavlink not generate go-sources