Refactor rotatelogs to allow easier implementation

of signal triggered log rotation.

- move code into new functions checkRotate() and doRotate()
- bundle config data and runtime data in two structs to
  allow easier passing to functions
- Simplify bypass_io logic as a first use case for doRotate
  and rename flag to force_open to reflect the new logic



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@733476 13f79535-47bb-0310-9956-ffa450edef68