plscheme - plscheme: In the previous versions, all user supplied

Log Message:
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In the previous versions, all user supplied procedure calls were getting
evaluted in the same environment of the current session. From now on, every
procedure will run in its own module scope. While this gives us ability to
preserve our environment between different execution contexts, on the other
hand, it causes an onstacle to preserve some specific variables during calls.
(Formerly, shared variables.) But we were supporting shared variables globally
per session and this was not a very useful feature. Namely, it is not a that big
loss.

Furthermore, with the availability of using module interface for user space code
execution, now PL/scheme supports trusted and untrusted PL modes that can be
configured with a --safe-r5rs flag to ./install.sh. (Or -DSAFE_R5RS to cc).

And added a small access() check for dataconv.scm. (Guile was doing this check
for us in a very ugly way.)

Modified Files:
--------------
    plscheme:
        README.plscheme (r1.9 -> r1.10)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/plscheme/plscheme/README.plscheme.diff?r1=1.9&r2=1.10)
        install.sh (r1.4 -> r1.5)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/plscheme/plscheme/install.sh.diff?r1=1.4&r2=1.5)
        plscheme.c (r1.21 -> r1.22)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/plscheme/plscheme/plscheme.c.diff?r1=1.21&r2=1.22)