std.database

[Erik Smith via Digitalmars-d]

I've made a few updates based on some of the feedback in this 
thread.

- execute() renamed to query()
- query with input binds directly from connection
- query() returns result for chaining

The design is still early stage.  I've got a growing list of 
design options which I'll bring into discussion once the 
interface becomes more stable.

Other updates:

- postgres reference implementation added (synchronous only at 
moment)
- DUB package now available as dstddb
- DMD "cyclic structs" bug fix may land soon (PR appeared) with 
design improvements to follow.

erik