Don't guard against mismatched saves/restores.

Let broken files be as broken as they are.

This reverts commit 8284008a.

Fixes #1395 (closed)

Not sure this is the perfect solution, but it is a solution. The revert was made manually due to subsequent changes - but i did not remove the added copyright.

The reverted commit seems to imply that it was guarding Poppler against untrusted streams, but i can only see that it guards the streams against themselves.