Escape special characters in Varnish::banPath() host patterns

[jdreesen]

Hostnames contain characters such as ., which should be escaped in a regex in order to match literally.

[dbu]

the documentation on the interface tells that if hosts is a string, it is expected to be a regex, but if its an array, its "exact host names". so this fix seems correct to me.

thanks for looking into it.

i would rather only change this in the 3.x branch, as 2.x is legacy at this point and 3.x the current version. this is not a security issue - it prevents unnecessary cache banning in an extreme edge cases where domain names only differ by a tiny bit. okay for you if i merge this to 3.x only?

[jdreesen]

Yes, we're still working on the 2.x branch, but we're not currently using this function. We have just discovered it during a review.

I'll rebase onto 3.x.

[dbu]

i fixed the build in the 3.x branch and added a changelog in #592