GIT 1.3.0-rc3

I do not think there are any more remaining major issue for a
real 1.3.0, so here is hopefully the final round of rc.  Testing,
fixing and polishing are appreciated.

Changes since v1.3.0-rc2 are as follows:

* documentation (Francis Daly, Jon Loeliger, Marco Roeland)
* add regexp to pickaxe (Petr Baudis)
* add git-clean (Pavel Roskin) 
* cvsimport fix (Johannes Schindelin)
* svnimport fix (Karl Hasselström)
* imap-send updates (Mike McCormack)
* assorted build and porting fixes (Johannes Schindelin)
* gitk updates (Keith Packard, Mark Wooding, Paul Mackerras, Pavel Roskin
  Rutger Nijlunsing, Stephen Rothwell)
* http-fetch can use PROPFIND in place of objects/info/packs (Nick Hengeveld)
* deltifier bounds safety (Nicolas Pitre)
* clone fix
* fix blame, broken by recent revision walker updates
* use built-in-xdiff in combine-diff
* use built-in-xdiff in blame
* support -S in blame
* diff_flush() memory leak fix when NO_OUTPUT
* make human-date parsing friendlier to our European friends.
* optimize thin-pack generation by pack-objects