Remove default settings from Doxygen config.

The set of supported Doxygenfile keys changes from release
to release, often resulting in warnings about needing to
upgrade the configuration file. However, this isn't
practical given the various versions different developers
have installed.

However, for the vast majority of keys we just want the
default values, so instead only include the keys we've
specifically set and let doxygen fall back to defaults
for all the rest.
1 file changed