* build: remove -Wabi and add -Wundef
gcc >= 8 throws a warning about -Wabi (without a specific ABI version)
being ignored, while -Wundef seems more useful (as shown by the change
in config.h, which was probably an unfortunate typo)
travis.yaml should probably be updated soon, but was left out from this
change as the current images don't yet need it
* lib: unused function in valueflow
refactored out since 8c03be32122ed85af89050eb1ad07ddd7038508e
lib/valueflow.cpp:3124:21: warning: unused function 'endTemplateArgument' [-Wunused-function]
* readme: include picojson
* make: also clean exe
bf5c71bdca