0.15 feature freeze

[Doug Cutting]

The 0.15 feature freeze will soon take effect.  No patches will be 
accepted for 0.15 unless they are either:

- "blocker" regressions, bugs that break important functionality;
- documentation improvements
Let's delay branching for 0.15 and hold off committing 0.16 patches to 
trunk for a week or so.  That way we can avoid having to merge all the 
blockers and documentation improvements to the branch, when they are 
likely to vastly outnumber the 0.16-bound commits for this period.  Okay?

Doug