[Rd] R_SHARE_DIR not defined for use in tests/Makefile running under Windows

[Tony Plate]

The make variable $(R_SHARE_DIR) seems to be available for use in 
tests/Makefile when running under Linux, but not Windows (R-2.6.2, R-2.6.1, 
R-2.7.0 alpha 2008-04-06, under Windows XP 64 bit, built locally for 32 bit).

Is this intentional, or an oversight?  Is it OK to use $(R_HOME)/share 
instead (seems to work OK)?

I notice the following in /src/gnuwin32/front-ends/rcmdfn.c (from R-alpha 
2008-04-06), which would suggest that the intention was that R_SHARE_DIR 
should be defined... (and I assume it would propagate to to be available in 
a Makefile.)

int rcmdfn (int cmdarg, int argc, char **argv)
{
     /* tasks:
        find R_HOME, set as env variable
        set R_SHARE_DIR as env variable
        set PATH to include R_HOME\bin
        set PERL5LIB to %R_SHARE_DIR%/perl;%Perl5LIB%
        set TEXINPUTS to %R_SHARE_DIR%/texmf;%TEXINPUTS%
        set HOME if unset
        launch %R_HOME%\bin\$*
      */

-- Tony Plate