Stacking originally seemed like a good idea, but perhaps this does read a
bit better (and looks more like the composition operation being applied),
and composes a bit better if we needed e.g. \bicomp\bicomp{R}.
It's also less ambiguous when it's over a larger expression. For example,
\bicomp{[A]} places \circ over top of the A, which looks as if it's
[\bicomp{A}]. It's obvious what the intention is in that context, since
\bicomp{A} makes no sense, but there could be other situations where it
doesn't. With this change, it results in {[A]}^\circ.
Mike Gerwitz
8d1c29b4cc