FastR Grid: devices that save images support %d placeholder for filenames.

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

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

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

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

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

...e/r/library/fastrGrid/device/awt/BufferedImageDevice.java

...racle/truffle/r/library/fastrGrid/grDevices/DevCairo.java

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

...fle/r/library/fastrGrid/grDevices/InitWindowedDevice.java