Messaging API v2
This patch series is a new version of the messaging API patches. It mainly fixes issues observed in the previous version, in particular:
- (Un)Escaping is now done using pa_escape()/pa_unescape()
- The boolean is_unpacked parameter has been removed from public functions
- Split_list() is now internal
- All read functions except read_raw() preserve a default value on failure
- Many smaller fixes and documentation updates
Patches 2 - 5 (1 - 4 from the old series) are nearly unchanged and were OK in the previous review.