encoding: move case-related utils up
This will be useful for the next commit that needs this code earlier.
Differential Revision: https://phab.mercurial-scm.org/D11024
dirstate: drop the last explicit `state` usage in the module
The internal detail of the `state` bytes is not longer exposed to the dirstate
layer.
Differential Revision: https://phab.mercurial-scm.org/D10977
test: use a python script in `test-transaction-rollback-on-sigpipe.t`
This still does not work on Windows, but at least this is a python script now.
Differential Revision: https://phab.mercurial-scm.org/D10947