Get rid of Policy.ref_alloc, comment is always heap-allocated
Rename comment field in Promise to be called 'comment'
Policy.has_subbundles is not a part of 'runtime bus'
Remove unused file_classes field from EditContext
Remove unused empty_first field from EditContext
Check if the have a good bundle statement + unit test
Ensure that comment is always heap-allocated
Stop abusing Promise.this_server in edit_{line,xml}
Implement per-promise parse-tree syntax/semantic check hook

This hook allows to modularize pre-evaluation checks and in particular split out
significant chunks out of policy.c. Further, it allows to move some promise-type
level checks currently being done during evaluation to parse-time.
Unexport PromiseHash, it's only used for locks
Merge pull request #510 from basvandervlies/promise_type_checking

Check if we have a good bundle statement + unit test
Stand-alone template rendering, does not spawn edit_line promises.