Merge branch 'ns/core-fsyncmethod' into ns/batch-fsync

Merge branch 'ns/core-fsyncmethod' into ns/batch-fsync

* ns/core-fsyncmethod:
  configure.ac: fix HAVE_SYNC_FILE_RANGE definition
  core.fsyncmethod: correctly camel-case warning message
  core.fsync: fix incorrect expression for default configuration
  core.fsync: documentation and user-friendly aggregate options
  core.fsync: new option to harden the index
  core.fsync: add configuration parsing
  core.fsync: introduce granular fsync control infrastructure
  core.fsyncmethod: add writeout-only mode
  wrapper: make inclusion of Windows csprng header tightly scoped