other things are starting to use this, so I need to move it;
I was using the wrong comment character - oops (fixed);
added test code;
(member? ...) is now in "common.scheme";
(atom? ...) was already in "common.scheme";
(member? ...) was rewritten to use (equal? ...) when it was moved to "common.scheme";
moved (multirember ...) because other stuff is starting to use it now;
modified to use (multirember ...), so that the first occurrence is preserved rather than the last;
my original version worked the same, so I'm reverting back to that, for fun;