Interaction enumeration

Represents increasing amounts of user interaction.

Members

Member name	Description
`BATCH_MODE`	Omits all stops and omits terminal output.
`NONSTOP_MODE`	Omits all stops.
`SCROLL_MODE`	Omits error stops.
`ERROR_STOP_MODE`	Stops at every opportunity to interact.
`FORMAT_DEFINED`	Preserves the interaction mode defined by a TeX format.