describe_table does not detect broken synonyms

[bhenderson]

I'm not sure how to run the tests, but I believe it's looking for an actual oracle install, which I don't have.

The issue that I came across was that our database had a table renamed, but the synonym was not updated. When I tried doing a desc on the synonym in sqlplus I got an error (I believe the error was "circular synonym". The problem has been fixed, so I can't repro now), but our app would get stacklevel too deep.

The issue is in #describe_table https://github.com/kubo/ruby-oci8/blob/master/lib/oci8/metadata.rb#L2015

[kubo]

Thank you for your report. I have fixed it.