[1.5.x] Corrected the section identifier for MySQL unicode reference.

Backport of b2514c02e1 from master
[1.5.x] Fixed a remote code execution vulnerabilty in URL reversing.

Thanks Benjamin Bach for the report and initial patch.

This is a security fix; disclosure to follow shortly.

Backport of 8b93b31487d6d3b0fcbbd0498991ea0db9088054 from master
[1.5.x] Prevented leaking the CSRF token through caching.

This is a security fix. Disclosure will follow shortly.

Backport of c083e3815aec23b99833da710eea574e6f2e8566 from master
[1.5.x] Fixed queries that may return unexpected results on MySQL due to typecasting.

This is a security fix. Disclosure will follow shortly.

Backport of 75c0d4ea3ae48970f788c482ee0bd6b29a7f1307 from master
[1.5.x] Added information on resolved security issues to release notes.

Backport of c07f3e60c2d455e36ba4ac339d4283d32bbc3814 from master
[1.5.x] Update for 1.5.6 security release.
[1.5.x] Add missing disclosure information to security archive.