Various constants and utilities used when parsing the ILASM format for IL

Diagnostics from the AbsIL toolkit. You can reset the diagnostics stream to point elsewhere, or turn it off altogether by setting it to 'None'. The logging channel initially points to stderr. All functions call flush() automatically. REVIEW: review if we should just switch to System.Diagnostics

The "unlinked" view of .NET metadata and code. Central to the Abstract IL library