unify interop exception handling in FFI

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

.../com/oracle/truffle/r/ffi/impl/llvm/TruffleLLVM_Call.java

...m/oracle/truffle/r/ffi/impl/llvm/TruffleLLVM_PkgInit.java

...com/oracle/truffle/r/ffi/impl/llvm/TruffleLLVM_Stats.java

...com/oracle/truffle/r/ffi/impl/llvm/TruffleLLVM_Tools.java

...m/oracle/truffle/r/ffi/impl/llvm/TruffleLLVM_UserRng.java

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

...com/oracle/truffle/r/ffi/impl/nfi/TruffleNFI_PkgInit.java

...c/com/oracle/truffle/r/ffi/impl/nfi/TruffleNFI_Tools.java

...com/oracle/truffle/r/ffi/impl/nfi/TruffleNFI_UserRng.java