zsh 5.2 release

This is a stable release. There are many bug fixes and a few minor new features since 5.1.1.
This release includes .asc files containing a detached signature for each tar ball. The signature is for the key 2048R/4BDB27B3 (Peter Stephenson <p.w.stephenson@ntlworld.com). You can find it on the keyserver at pool.sks-keyservers.net.