c_config: cleanup directory after configuration if no cache is needed.
Enable case-insensitive Node lookup
qt5: added qtmain to the possible lib

on Windows, build with QTMAIN and subsystem="windows" to create a Qt app without the console, Qt will use your "main" and manage the "WinMain" for you.
boost: on Windows, install DLL for libs linked dynamically.

It will only install DLL when waf is called with the "install" parameter, and will install the DLL in the install directory.
If the user wants to run his exe in the build dir, I'd recommend setting boost lib in the PATH.
boost: find_file throw an exception is the file isn't found.
fixed --make-waf with python3