MINIFICPP-276: Add EXCLUDE_BOOST option

[phrocker]

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[ai-christianson]

LGTM, however I suspect any boost at all may be more trouble than it's worth, given our current minimal coupling with it.

I would be open to keeping boost for future extensions if there is a compelling case for it, and then sequestering it to extensions which are implicitly disabled if EXCLUDE_BOOST is set.