lang/mlton: Fix BUILD

• Memory usage has been so extreme that building on i386 build servers often fails due to slightly imperfect conditions. This is like because the zone pass was intended to be disabled on modern versions, but was unintentionally? hardcoded to a specific older version (corrected).
• Simple fix where bootstrap images for FreeBSD versions >= 13 were unavailable (if compat13x is needed, then I will add it to dependencies, but it shouldn't be necessary), so it should build on FreeBSD 14.x with this change
• While I(bofh) am here pet portclippy/portfmt
• Utilize OPTIONSNG as best as possible

PR: 261820
Approved by: MAINTAINER