rffi: refactor more RFFI interfaces into one Node per function

...acle/truffle/r/engine/interop/ffi/llvm/TruffleLLVM_C.java

...ruffle/r/engine/interop/ffi/llvm/TruffleLLVM_CAccess.java

...e/truffle/r/engine/interop/ffi/llvm/TruffleLLVM_Call.java

...le/truffle/r/engine/interop/ffi/llvm/TruffleLLVM_DLL.java

.../truffle/r/engine/interop/ffi/llvm/TruffleLLVM_Stats.java

.../src/com/oracle/truffle/r/library/graphics/RGraphics.java

.../src/com/oracle/truffle/r/library/grid/GridFunctions.java

...ary/src/com/oracle/truffle/r/library/tools/C_ParseRd.java

...rary/src/com/oracle/truffle/r/library/tools/DirChmod.java

com.oracle.truffle.r.native/fficall/src/jniboot/jniboot.c

...oracle/truffle/r/nodes/builtin/base/DynLoadFunctions.java

...om/oracle/truffle/r/nodes/builtin/base/FileFunctions.java

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

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

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

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

.../com/oracle/truffle/r/nodes/builtin/base/foreign/Fft.java

...le/r/nodes/builtin/base/foreign/FortranAndCFunctions.java

...om/oracle/truffle/r/runtime/ffi/generic/Generic_Grid.java

...m/oracle/truffle/r/runtime/ffi/generic/Generic_Tools.java