[GR-5543] [GR-5541] Many improvements and bug fixes concerning parallel execution.

...fle.r.engine/src/com/oracle/truffle/r/engine/REngine.java

...ffi.impl/src/com/oracle/truffle/r/ffi/impl/jni/JNI_C.java

....impl/src/com/oracle/truffle/r/ffi/impl/jni/JNI_Call.java

...l/src/com/oracle/truffle/r/ffi/impl/nfi/TruffleNFI_C.java

...rc/com/oracle/truffle/r/ffi/impl/nfi/TruffleNFI_Call.java

.../truffle/r/library/fastrGrid/FastRGridExternalLookup.java

...in/src/com/oracle/truffle/r/nodes/builtin/base/APerm.java

.../com/oracle/truffle/r/nodes/builtin/base/BasePackage.java

...com/oracle/truffle/r/nodes/builtin/base/RNGFunctions.java

...rc/com/oracle/truffle/r/nodes/builtin/base/Transpose.java

.../nodes/builtin/base/foreign/CallAndExternalFunctions.java

...e/truffle/r/nodes/builtin/base/foreign/LookupAdapter.java

...om/oracle/truffle/r/nodes/builtin/fastr/FastRContext.java

.../oracle/truffle/r/nodes/access/BaseWriteVariableNode.java

...e/truffle/r/nodes/access/WriteLocalFrameVariableNode.java

...e/truffle/r/nodes/access/WriteSuperFrameVariableNode.java

...le/truffle/r/nodes/access/variables/ReadVariableNode.java

...ruffle/r/nodes/access/vector/CachedReplaceVectorNode.java

...s/src/com/oracle/truffle/r/nodes/binary/CastTypeNode.java

...s/src/com/oracle/truffle/r/nodes/builtin/CastBuilder.java