Bump version number to 3.3.1

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branch : release-3.3
Update release notes

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branch : release-3.3
Update year 2012 -> 2013

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branch : release-3.3
Quick fix for GC breakage after changes in Cython 0.18

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branch : release-3.3
extra : source : 0c09069d6cee20cd01683303c15318cd5d6e0732
Update after changes in petsc-dev
Added tag 3.3.1 for changeset 8943ef07f943

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branch : release-3.3
Merge branch release-3.3