* Harden compiler against exceptions during stream dispose

It's possible (likely even) for one of the streams the compiler uses for
output files will throw during disposal. Currently this crashes the
compiler. This change adds a wrapper type around stream to catch
exceptions during disposal and report them as diagnostics instead.

Fixes https://devdiv.visualstudio.com/DevDiv/_workitems?id=217719

* Add VB tests

* Respond to PR comments

* Respond to PR comments

* Respond to PR comments

* Conform to style guidelines