retire the use of JNR, convert to plain JNI, some refactoring for clarity

com.oracle.truffle.r.native/Makefile

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

com.oracle.truffle.r.native/fficall/src/jni/Parse.c

com.oracle.truffle.r.native/fficall/src/jni/Rdynload_fastr.c

com.oracle.truffle.r.native/fficall/src/jni/Rembedded.c

com.oracle.truffle.r.native/fficall/src/jni/Rinternals.c

com.oracle.truffle.r.native/fficall/src/jni/appl_rffi.c

com.oracle.truffle.r.native/fficall/src/jni/base_rffi.c

com.oracle.truffle.r.native/fficall/src/jni/c_rffi.c

com.oracle.truffle.r.native/fficall/src/jni/call_rffi.c

com.oracle.truffle.r.native/fficall/src/jni/lapack_rffi.c

com.oracle.truffle.r.native/fficall/src/jni/misc_rffi.c

com.oracle.truffle.r.native/fficall/src/jni/pcre_rffi.c

com.oracle.truffle.r.native/fficall/src/jni/rffiutils.c

com.oracle.truffle.r.native/fficall/src/jni/rffiutils.h

com.oracle.truffle.r.native/fficall/src/jni/stats_fft.c

com.oracle.truffle.r.native/fficall/src/jni/userrng_rffi.c

com.oracle.truffle.r.native/fficall/src/jni/zip_rffi.c

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

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