Move ax11*, a12* to classical logic section.
Move ax11*, a12* to classical logic section.

If these make any sense at all here, it would be in the
classical logic section, as most of them do depend on ax-3.

Theorems moved: ax11f, ax11indn, ax11indi, ax11indalem, ax11inda2ALT,
ax11inda2, ax11inda, a12stdy1, a12stdy2, a12stdy3, a12stdy4, a12lem1,
a12lem2, a12study, a12studyALT, a12study2, a12study3.

metamath/set.mm,metamath/set.mm,metamath/set.mm