e-base.bbclass: bump EFL_SRCREV for E17 alpha4

e-base.bbclass: bump EFL_SRCREV for E17 alpha4

* be aware that this rev is slightly newer then alpha4, because we
  need backported patch to edje-1.7
  r79484 | raster | 2012-11-21 00:58:03 +0100 (Wed, 21 Nov 2012) | 3 lines
  backport cedrics fix... not backported when done! :-P
  and also this works only with conf/distro/include/efl-from-svn-recipes.inc
  otherwise edje_cc segfaults when building default e-wm theme

(From meta-openembedded rev: 84ac2a95e2eb18e8265ffc61dd6df33e42f61b7f)

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>