[bigfix] circular-list?

Fix a bug in circular-list?
[bugfix] circular-list? in srfi-1

circular-list? does not get stuck in an infinite loop if it is given a list such as '(1 2 3 2 3 2 3 2 3 ...).
Merge pull request #72 from koba-e964/master

[bugfix] circular-list?, proper-list?