NEW IN WAF 2.0.0 (preview 1)
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* Provide a new priority system to improve scalability on complex builds
* Provide TaskGroup objects to improve scalability on complex builds
* Force new files into the build directory by default (use Node objects to bypass)
* Built-in support for building over UNC paths
* Simplify the Task class hierarchy; TaskBase is removed
* Display commands as string with "WAF_CMD_FORMAT=string waf build -v"
* New ant_glob(..., generator=True) now returns a Python generator
* Accept nested lists and generators in bld(source=...)
* Sort TaskGen methods in alphabetical order by reversing TaskGen.prec order

* Remove 'ut_fun' from waf_unit_test.py
* Remove Node.sig and Node.cache_sig
* Remove the BuildContext.rule decorator
* Remove Task.update_outputs, Task.always_run
* Remove atleast-version, exact-version and max-version from conf.check_cfg
* Remove c_preproc.trimquotes
* Remove field_name, type_name, function_name from conf.check() tests
* Remove extras/mem_reducer.py as a better solution has been merged