HEADS UP: SIP v6.7.0 Snapshots

[Phil Thompson]

The current SIP v6.7.0 snapshot is the next stage of migrating SIP to a 
pure Python implementation. As with the replacement of the old parser in 
v6.6.0...

- the new code is slower (for now)
- error reporting is improved
- the generated code should be identical to that generated by earlier 
versions
- it builds PyQt correctly but PyQt does not use all the functionality.

Other projects that use SIP (eg. wxPython, QGIS) should test and report 
problems.

Phil