Linux specific fixes in FastR/LLVM

ci.hocon

...oracle/truffle/r/ffi/impl/common/JavaUpCallsRFFIImpl.java

...c/com/oracle/truffle/r/ffi/impl/interop/package-info.java

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

...c/com/oracle/truffle/r/ffi/impl/llvm/TruffleLLVM_DLL.java

.../truffle/r/ffi/impl/llvm/TruffleLLVM_UpCallsRFFIImpl.java

...rc/com/oracle/truffle/r/ffi/impl/upcalls/FFIWrapNode.java

com.oracle.truffle.r.native/fficall/Makefile

com.oracle.truffle.r.native/llvm_tools/llvm-c++

com.oracle.truffle.r.native/llvm_tools/llvm-cc

com.oracle.truffle.r.native/llvm_tools/llvm-helper

com.oracle.truffle.r.native/run/edMakeconf.etc.llvm

...time/src/com/oracle/truffle/r/runtime/data/RPairList.java

documentation/dev/truffle_llvm_ffi.md