Merge branch 'dalcinl/opthandlers-destroy' into maint

* dalcinl/opthandlers-destroy:
  Fix PetscObjectDestroyOptionsHandlers() to support missing destroy function
release: fix missing release string in changes/34.html
setup.py: update for the new release naming scheme
Mat doc: align columns in preallocation diagrams

Noticed-by: Mikael Öhman <micketeer@gmail.com>
changed final argument to PetscPClose from PetscInt to int since this is an in returned from a system call
build/nightlyscripts: checkout required branch as 'detached'
so the builds are tolerant to deleted/recreated branches
Merge branch 'maint'
Merge branch 'balay/scripts-use-git-detached-head'