[GR-3344] FastR Grid emulation: support device hold/flush functions.

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

...rary/src/com/oracle/truffle/r/library/fastrGrid/GPar.java

...c/com/oracle/truffle/r/library/fastrGrid/GridContext.java

...src/com/oracle/truffle/r/library/fastrGrid/GridState.java

...y/src/com/oracle/truffle/r/library/fastrGrid/LPoints.java

...ffle/r/library/fastrGrid/device/BufferedJFrameDevice.java

...le/truffle/r/library/fastrGrid/device/DrawingContext.java

...le/r/library/fastrGrid/device/DrawingContextDefaults.java

.../oracle/truffle/r/library/fastrGrid/device/GridColor.java

...oracle/truffle/r/library/fastrGrid/device/GridDevice.java

...acle/truffle/r/library/fastrGrid/device/JFrameDevice.java

...e/truffle/r/library/fastrGrid/grDevices/DevHoldFlush.java