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More improvements to boolean tools. The main change (although very little in
code) is changing fuzzy comparisons of floating point values. For testing, a
new define is added in intern/boolop/intern/BOP_MathUtils.h called
VAR_EPSILON, which enables better comparisons. This is turned on by default;
undefining it will revert to using the previous comparisons. The downside of
these new comparisons is a loss in speed, but the resulting meshes are more
likely to be manifold (although still not always).
The other changes include speed improvements based on profiling results and
fixes for the improper creation of triangular faces with only two vertices.
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Bugfix #6847: Previous fix for "spikes" when using booleans caused creation
of faces with only two unique vertices ("eekadoodles"). This patch cleans up
the test for triangles with near-colinear vertices so PHANTOM faces can be
used again, and also adds a hack for now which removes any eekadoodle faces.
I haven't figured out yet exactly how the faces are being created; if I can
do so and fix it the hack will be removed.