Merge pull request #312 in G/fastr from...

Merge pull request #312 in G/fastr from ~STEPAN.SINDELAR_ORACLE.COM/fastr:feature/deferred-refcouting to master

* commit 'ef9010a1':
  Fix stylecheck issue
  ListBuiltin and Quote: make share permanent only when cached.
  ListBuiltin and Quote: handle sharing properly
  Reference counting for list elements
  Various tests for lists reference counting
  WriteIndexedVectorNode: only increment ref count for shareable, do not copy
  Fix UpdateDimNames: use the result of getNonShared()
  only increase element's refcount during list updates if necessary (if element changes)
  tests for list element duplication