Create a hook 'post-initialize' for people that want to define
something (perhaps in loader.rc.local) that can read in .conf files
after all the other .conf files have been read and override settings
in them. This is quite handy if the .conf file name is determined
while the loader is running, but might be generically useful for other
things. If this hook exists, call it, otherwise don't do anything.

Doing it in these functions ensures that this file is reliably
read. It also works around a defect in forth where s" isn't allowed
outside a function (well, in a compile context) leading to gross
workarounds if one were to hack loader.rc like:

: maybe-some-func s" some-func" sfind if execute else drop then ;
maybe-some-func

which somehow seems worse. Though I'm sure there's some clever forthy
way of doing that with a macro.

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