R-devel changes on allowed C-API

[llrs]

On CRAN rlang has a warning and is set for archiving by 2025-11-27.

Result: WARN 
  File ‘rlang/libs/rlang.so’:
    Found non-API calls to R: ‘ENCLOS’, ‘OBJECT’, ‘PRENV’, ‘PRVALUE’,
      ‘R_PromiseExpr’, ‘Rf_allocSExp’, ‘Rf_findVarInFrame3’, ‘SETLENGTH’,
      ‘SET_BODY’, ‘SET_CLOENV’, ‘SET_ENCLOS’, ‘SET_FORMALS’,
      ‘SET_GROWABLE_BIT’, ‘SET_OBJECT’, ‘SET_TRUELENGTH’, ‘SET_TYPEOF’,
      ‘XTRUELENGTH’
  These entry points may be removed soon:
  ‘SET_ENCLOS’, ‘ENCLOS’, ‘OBJECT’, ‘SET_TYPEOF’

I don't see any recent issue about this, but I think the team is aware since:

• Non-API calls conundrum #1706
• Remove SET_ENCLOS() usage #1707
• Probably also aware of the email sent to r-devel mailing list.

Note: SET_OBJECT isn't mentioned on the above issues but using it triggers the warning.

Many thanks for developing and maintaining the package! I hope these are easy to replace/fix.