The 'Fabien-Constants' branch has just been merged into the trunk in the SVN repository. This release is at an early Alpha state, not ready to be downloaded to your project dirs.
Please, for the users of the symfony SVN, do not upgrade to the revision 356. We will soon release a Beta version of the 0.6 release, ready to test, but we know that the current release is not stable enough yet. The latest nightly build remains the 0.5.284, until the release of the Beta. PEAR users should not be proposed to upgrade to the Alpha anyway.