bettermc 1.1.2

Misc

• work around an issue in base R w.r.t. source references and lazy loading as discussed in https://r.789695.n4.nabble.com/memory-consumption-of-nested-un-serialize-of-sys-frames-tp4768465.html
• prepare for upcoming changes to Rinternals.h
  • do no longer assign to ATTRIB() and OBJECT()
  • do no longer depend on SEXPREC_ALIGN