Proposal

Add the following to table 3.5: 
String           Value data type  Constant?
X:deferred              -           -       string present only if DEFER, DEFER@, DEFER!, IS and ACTION-OF are present
X:extension-query       -           -       string present
X:parse-name            -           -       string present only if PARSE-NAME is present
Add the following to table 15.1: 
X:defined               -           -       string present only if [DEFINED] and [UNDEFINED] are present
Append in Section 2.2.4.1: 
- ENVIRONMENT? string if the word belongs to a Forth200x extension.