shib_auth 6.x-4.2-rc1

This version fixes a couple of minor bugs that were fixed long time ago without an official release:

• #1401634: Handle safe header variables on IIS
• #1366700: Not generating login block because anonymous-user check too strict
• #1589006: Potential syntax/logic error in shib_auth_form_alter() forcing unexpected session creation and preventing caching

Testers are welcome. Because the changes are so minor, it is expected that this release will turn to 6.x-4.2 in a relatively short time.