Err, is this really fixed in 2.21? I can't find it anywhere in 2.32.3 
(debian unstable)

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I just did a `--dumpsetup` with the current version from the Git repository
and the default option is

    # use '!'-prefixed preprocessor directives?
    prefix_directives => 0,

My impression was that this should be enabled by default now.  --[[JasonBlevins]]