Don't expose `::util::` symbols

[Eyal Rozenberg]

Our library currently exposes symbols in the ::util:: namespace, which are only used internally. That shouldn't happen - others might want to use those names.

Here's an SO question about this issue..

For now, let's use a workaround - move a lot of the utility code into a nameapace - avoiding accidental dependencies by outside source but not making the symbols actually private.