Modifies test suites to document compatibility with https://github.com/RainwayApp/bebop
-- These tests cover compilation compatibility, not wire format compatibility, yet.
Smaller changes:
Empty enum definitions will no longer generate an empty const block.
Negative field numbers for messages and unions will be caught at compile time as errors.
Fixed a bug with line and column numbers output by the compiler in error strings.
In progress, resolves #9