[Rd] include <R.h>

[Paul Gilbert]

I am trying to add

#include <R.h>

to a .c file in one of my package, so I can call error() without a 
complaint about implicit defined function. The src/ has a Makefile, to 
build some exec/ files that are needed. Without the include, my Makefile 
target

OBJS = $(SRC:.c=.o)

$(PKGNAME).so: $(OBJS) rpcx.h
	$(R_HOME)/bin/R CMD SHLIB  $(OBJS)

seems to work fine, and I do not need a target for the .o's, the default 
works. But when I add the include, the location of R.h does not get 
passed along. How am I suppose to specify $(R_HOME)lib/R/include so that 
it gets passed along by R CMD SHLIB ?

Paul