Waf 2.1
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- Remove Winphone/WinCE detection in msvc.py
- Fix the circular imports ccroot<->c_config.py
- Remove superfluous *k in ctx.load() and other unused parameters
  Ensure conf.load() has the same interface as ctx.load()
- Remove waflib.Runner.PriorityTasks.appendleft
- Remove waflib.Task.TaskBase
- Remove the upper class of waflib.Task.Task (metaclasses)
- Ordered_iter_dict in python 3.7
- Change _add_task to add_task in Runner.py