R-1374 Unsupported interpreter version 4.2.0

Several C Headers were moved from public include to internal Defn.h file.

See R sources commit: 86b4a0641e889808ce204e28dd8bd19bbd1c8cbb
Move a number of non-API declarations and macro definitions from the
installed header Rinternals.h to the private header Defn.h.
git-svn-id: https://svn.r-project.org/R/trunk@80644 00db46b3-68df-0310-9c12-caf00c1e9a41

GitOrigin-RevId: f27d85dec0bf5c48bcf5fd3847e1e9d85759f9ee