rffi: rewrite all global variables to function calls

com.oracle.truffle.r.native/fficall/src/include/Defn.h

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

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

...ruffle.r.native/fficall/src/variable_defs/variable_defs.h

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

com.oracle.truffle.r.native/include/ed_GraphicsEngine

com.oracle.truffle.r.native/include/ed_Rinterface_gcntx

com.oracle.truffle.r.native/include/ed_Rinterface_variables

com.oracle.truffle.r.native/include/ed_Rinternals

...i/src/com/oracle/truffle/r/runtime/ffi/RFFIVariables.java

mx.fastr/mx_fastr.py

mx.fastr/mx_fastr_edinclude.py

mx.fastr/mx_fastr_mkgramrd.py