Impacts of Executor handling of 2a

[JosepMariaBlasco]

Legacy programs are impacted when

• <after number> is a valid variable symbol and the NOVALUE condition is enabled.
• A label starts with a number

The second item is too restrictive. All contexts in which a taken_constant is allowed are also affected. This includes labels, but also message names, user condition names, trap names, function and procedure names, annotation names, annotation values (when symbols), class, metaclass, mixin class, subclass, and inherited classes in ::CLASS directives, ::CONSTANT names, ::CONSTANT values (when symbols), ::METHOD names, ::REQUIRES program names, namespace names, ::RESOURCE names, ::RESOURCE end delimiters, ::ROUTINE names, ...