Add initial token to eliminate special handling of first token and to enable all token processing in while (next()) loops

Problem/Motivation

Add initial token to eliminate special handling of first token and to enable all token processing in while (next()) loops. Currently, the first token is processed and then looping begins on the rest of the tokens. Adding an initial token allows removal of exception code and simplifies processing of tokens. This change will also facilitate another change in a subsequent issue.

Proposed resolution

See patch(es).

Remaining tasks

Before committing, code will be reviewed, tested against D8 core files, and documentation updated.

User interface changes

Not applicable.

API changes

To be completed later.