Sessions could not be save for empty workspaces since LoadSaveFunctions.SaveToConn expected a non-empty list of variables to store. However, GnuR allows to do so.
Also fixed problem when using function "q()" in test cases which caused the test suite to crash due to an unexpected but legitimate exception.

* commit '57201a87':
  Configure unit tests to not load saved sessions (.Rdata/.Rhistory)

* commit '1b7db628':
  add back JNI_Base TruffleBoundary

Merge pull request #668 in G/fastr from ~MICK.JORDAN_ORACLE.COM/fastr:feature/baserffi-refactor to master

* commit '942b6a66':
  rffi: refactor more RFFI interfaces into one Node per function
  rffi: refactor BaseRFFI into one node per function

Merge pull request #652 in G/fastr from ~STEPAN.SINDELAR_ORACLE.COM/fastr:feature/grid-support to master

* commit '51a8d559':
  Initial grid package support
  Fix: make tests independent on whether grid package is loaded or not

Merge pull request #675 in G/fastr from ~STEPAN.SINDELAR_ORACLE.COM/fastr:fix/range-honors-finite-arg to master

* commit 'd19add0a':
  range honors the 'finite' parameter

Merge pull request #664 in G/fastr from ~LUKAS.STADLER_ORACLE.COM/fastr:feature/visible_execute to master

* commit '2bee338b':
  introduce visibleExecute and use whereever visibility is required

Merge pull request #669 in G/fastr from ~MICK.JORDAN_ORACLE.COM/fastr:feature/rffi-remove-gvars to master

* commit 'bb6d88bc':
  rffi: remove unused global variables

Note: for some classes used in the tests like 'unit' grid adds S3 methods,
which are not removed even if the package is unloaded.

* commit 'b587e7da':
  rfffi: simplify factory creation

Merge pull request #665 in G/fastr from ~STEPAN.SINDELAR_ORACLE.COM/fastr:feature/paste-s3-dispatch to master

* commit '599c4c23':
  Fix: forgotten ProfiledCastNode in Quantifier
  paste and paste0 use as.character internally

Merge pull request #672 in G/fastr from ~LUKAS.STADLER_ORACLE.COM/fastr:feature/remove_materialize_shared to master

* commit '72ac8c95':
  don’t use sequences in vector fast paths

* commit '49468004':
  added builtin function "is.single"

* commit '28e7013d':
  typos in documentation

Merge pull request #662 in G/fastr from ~LUKAS.STADLER_ORACLE.COM/fastr:feature/force_dispatch_args to master

* commit '0e08476d':
  force promises in special call arguments where dispatch would force them anyway

Merge pull request #663 in G/fastr from ~LUKAS.STADLER_ORACLE.COM/fastr:feature/access_nodes to master

* commit '9bb8a7e1':
  AccessSlotNode and UpdateSlotNode don’t need to be RNodes

* commit '85a20b5d':
  CharSXPWrapper as TruffleObject
  rffi: rewrite all global variables to function calls

* commit 'f92513df':
  generated expected output messages
  c/rbind adds NULL dimnames even if not necessary
  deparse adds too many right parentheses when structure expressions has more attributes

Merge pull request #660 in G/fastr from ~LUKAS.STADLER_ORACLE.COM/fastr:feature/meta_tck_tests to master

* commit 'e3853c46':
  implement TCK tests for findMetaObject and findSourceLocation

* commit 'f038d78f':
  Sharing documentation converted to Markdown
  Cast pipelines documentation converted to Markdown