Merge branch 'jc/core-checkstat'

The configuration variable core.checkstat was advertised in the
documentation but the code expected core.statinfo instead.

For now, we accept both core.checkstat and core.statinfo, but the
latter will be removed in the longer term.

* jc/core-checkstat:
deprecate core.statinfo at Git 2.0 boundary

diff --cc config.c
Simple merge