libfive eigen 3.4 aligned alloc workaround

eigen 3.4 nops the new operator macro but they forgot that aligned new has a different signature than non-aligned. This also takes into account that we need to align our allocations, as this is not done by the default new.

This fixes https://github.com/issues/libfive/libfive/462 and https://github.com/issues/libfive/libfive/464