[SoC] QGIS on steroids - week #4

[Martin Dobias]

Hi all

This week I have reworked render caching mechanism to be more robust
and to be usable for threaded rendering.

Next week I'd like to address further issues of threaded rendering -
both within application GUI and locking in the core.
I'm not blocked on anything.

For more details (mainly about render caching) please check out the wiki page:
http://www.qgis.org/wiki/QGIS_on_steroids_GSoC_2010

happy hacking
Martin