Waf 1.9
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* Reduce the key size in bld.task_sigs
* Provide a more efficient ConfigSet implementation
* Ensure _cache.py are valid python files
* Set cflags in the beginning / cppflags at the end
* Remove qt4 from the default modules, rework qt5
* Remove Node.cache_sig
* Make lazy visual studio detection the default
* Do not cache waf tool detection
* Fix the vala detection
* Better consistency between check_cfg and check_cc variables
* Detect Clang by default on FreeBSD instead of gcc
* Use relative paths in apply_incpaths (and absolute ones when paths cross drives)
* Let run_once accept a list of *args
* Let more context commands depend on the configuration

and all other issues listed on https://github.com/waf-project/waf/issues

Done
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* Remove the split functions from Utils
* Remove the command called "update"
* Include the tool 'nobuild' by default