Work around database/sql not being able to write large uint64 values

Go's sql package has this extremely weird restriction of not allowing to store uint64 with the highest bit set:

- [Issue 6113:	database/sql: why can't you use uint64 with high bits set?](https://code.google.com/p/go/issues/detail?id=6113)
- [Comment on database/sql type limitations](https://groups.google.com/forum/#!topic/golang-nuts/fTNwEzFEFP4)

I needed a quick solution for a project, so I worked around this using the applied patch. It is tested with SQLite only.

Please decide if this is the right way to work around the issue and how to proceed from here.