VOXELRENDER: too many regions are extracted

[mgerhardy]

Changing a single voxel at 272, 199, 397 on map https://aos.party/view/342 results in 7 unneeded re-extractions.

only the last of the regions should be needed. We have to take care at the mesh size boundaries. See issue #165

ERROR: (0) Extract the meshes for 1 regions
ERROR: (0) region region[mins(ivec3(272, 199, 397)), maxs(ivec3(272, 199, 397))]
ERROR: (0) modified region: region[mins(ivec3(272, 199, 397)), maxs(ivec3(272, 199, 397))]
ERROR: (0) extract region: region[mins(ivec3(192, 128, 320)), maxs(ivec3(255, 191, 383))]
ERROR: (0) extract region: region[mins(ivec3(192, 128, 384)), maxs(ivec3(255, 191, 447))]
ERROR: (0) extract region: region[mins(ivec3(192, 192, 320)), maxs(ivec3(255, 255, 383))]
ERROR: (0) extract region: region[mins(ivec3(192, 192, 384)), maxs(ivec3(255, 255, 447))]
ERROR: (0) extract region: region[mins(ivec3(256, 128, 320)), maxs(ivec3(319, 191, 383))]
ERROR: (0) extract region: region[mins(ivec3(256, 128, 384)), maxs(ivec3(319, 191, 447))]
ERROR: (0) extract region: region[mins(ivec3(256, 192, 320)), maxs(ivec3(319, 255, 383))]
ERROR: (0) extract region: region[mins(ivec3(256, 192, 384)), maxs(ivec3(319, 255, 447))]