[PyQt] PyQt v3.18, v4.5 and SIP v4.8 Snapshots

[Phil Thompson]

I've switched the SIP, PyQt3 and PyQt4 snapshots to their respective
trunks.

There has been a *lot* of refactoring in preparation for implementing
various Roadmap changes. With these in place I expect to make rapid
progress with the Roadmap.

The internal SIP API version number has changed so it will be necessary to
rebuild anything that depends on them (eg. PyKDE, PyQwt). The API itself
(used by handwritten code) has several changes but the old (now deprecated)
parts will remain for the lifetime of SIP v4. If you want to support the
Roadmap's incompatible changes (like the removal of QString) then you will
need to use the new APIs. There may be other compatibility changes needed
(like using "const char *" instead of "char *") but these can be made and
still work with earlier versions of SIP.

Phil