This patch wraps the LLNG app with a middleware that ensures anything that leaves LLNG is a binary string, including header values, as per PSGI spec.
@maudoux: this will probably cause regressions for you, make sure you update macros to no longer use unicode2iso/iso2unicode, and review other UTF-8 related workaround you have done. There might also be some performance regressions
Since this is a breaking, but necessary change, I added a release note and a way for users to restore previous (but buggy) behavior