fix various warnings

...src/com/oracle/truffle/r/ffi/impl/llvm/TruffleLLVM_C.java

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

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

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

.../com/oracle/truffle/r/library/fastrGrid/GridTextNode.java

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

...racle/truffle/r/library/fastrGrid/LInitViewPortStack.java

...ry/src/com/oracle/truffle/r/library/fastrGrid/LLines.java

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

...om/oracle/truffle/r/library/fastrGrid/LUnsetViewPort.java

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

...ffle/r/library/fastrGrid/device/awt/Graphics2DDevice.java

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

...com/oracle/truffle/r/library/fastrGrid/graphics/CPar.java

.../truffle/r/nodes/builtin/EagerResourceHandlerFactory.java

...n/src/com/oracle/truffle/r/nodes/builtin/base/DoCall.java

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

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

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

...oracle/truffle/r/nodes/builtin/fastr/FastRSourceInfo.java