string::Parse, Glushkov and regexps

string::Parse might maybe try to return UnboundedRegExp by default.

There is no problem with formal regexps, but e.g. glushkov method indices are very different from the ones in Unbounded versions.

> execute $r1 | string::Compose -
#E + ((a*+#E) a b c + #0* + b* b + c a)* a
> execute $r2 | string::Compose -
#E + ((a*+#E) a b c + (#0* + (b* b + c a)))* a

Look into it, maybe the problem is only in glushkov indexate?