don't trim "RCS" that is part of longer dir name

don't trim "RCS" that is part of longer dir name

When a directory is specified on the command line and the program
is converting the names of the input files being processed into output
filenames, don't strip "RCS" off the end unless that's the full name of
the final directory in the input path.

(Before this fix, an input file named something like
"from_RCS/sourcefile,v" have produced an output path of
"from_/sourcefile".)