Automated checkin: version bump for fennec 21.0 release. DONTBUILD CLOSED TREE a=release

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branch : MOBILE210_2013050901_RELBRANCH
Added FENNEC_21_0_RELEASE FENNEC_21_0_BUILD2 tag(s) for changeset c5fd3574d1d1. DONTBUILD CLOSED TREE a=release

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branch : MOBILE210_2013050901_RELBRANCH