R 1.8.1 ./configure with "," in working directory (PR#5536)

REMARK
As I have seen, ``,'' is used as separator for the sed statements in
config.status. Would it be possible to use instead a character which
cannot be used in a pathname, e.g. ``;''?

What makes you think ';' cant be used in a pathname?

$ mkdir 'foo;bar'
$ ls -l
total 4
drwxr-xr-x    2 rowlings baz          4096 Dec  5 10:01 foo;bar

I think the only (printable ascii) character not allowed in Unix 
pathnames is '/'.

Barry