Base64-encoding makes sense

Sorry, I was with my head in a different branch. This class does not support serialize. (Though I will use base64 for that branch.)

Can one of the admins verify this patch?

I'll pick this up to update it for PHP7 and propose an RFC for it. Will keep your name on the commit of course.

I've rewritten this patch for PHP7 as master...sgolemon:pr-660 with a couple notable differences:

1. Rather than dtor the by-value object passed into hash_final (which won't quite do what you think it'll do), I've used hash->context as a marker of the object's "validity". Once the hash is finalized, context gets freed, and any further attempts to use the object will throw an error matching the previous "invalid resource" message (see attached test).
2. I didn't add the method API. I in fact marked the constructor as private. This is just to keep the migration focused on the type change. We can (and should) follow it up with another diff to add methods.

ping @sara, there are conflicts, I didn't look close, sorry if silly ...

@krokjoe The conflicts are on @realityking's original PR (this diff), which is against PHP5. My rewrite of it is over at master...sgolemon:pr-660

Comment on behalf of pollita at php.net:

To minimize confusion, I'm closing this PR. Please reference my branch (linked above) for the current patch.

Also... @krakjoe, not @krokjoe :p

@sgolemon Can you please also open a PR for your branch? Otherwise not possible to review.

@nikic Here ya go: #2309