1.1.3dev: Added repository attribute `sync_per_request`. Refs #11776.

The `[trac] repository_sync_per_request` option has been removed and an upgrade step handles the population of the `sync_per_request` attribute of each repository.


git-svn-id: http://trac.edgewall.org/intertrac/log:/trunk@13393 af82e41b-90c4-0310-8c96-b1721e28e2e2