Log Message:
Updated waf to 1.9.6.

NEW IN WAF 1.9.6
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* Display @argfile contents in msvcdeps #1831
* Enable configurable preprocessor cache sizes #1833
* Allocate lru cache entries lazily
* Let unity builds use relative paths for msys #1834
* Added --dump-test-scripts to the unit test module #1852
* Added a warning on ant_glob '.' uses #1853
* LaTeX configuration tests output results to config.log
* Accept functools.partial() as task rules #1865