Disable the boolean and modifier python tests.

These tests rely on the behavoir of the old boolean, down the the
exact values of coordinates and ordering of the output vertices.
Because I want the default behavior of boolean to be new boolean
in this branch, this is inconvenient. I will make these tests work
again if/when we merge with master. Probably by adding the flag
that invokes the old behavior to the tests.
New bevel is mostly tested by unit tests now, so disabling the
regression test for it is not a big deal.

Merge branch 'master' into newboolean

Fixed bug where normals were sometimes wrong after a difference op.

Needed to check for correct orientation of a face before reusing an
original face.
Also added another test case.

Add some more boolean unit tests.

Fix union of two disjoint meshes.

Also added unit test for that.

Merge branch 'master' into newboolean

Resetting some stuff that got messed up with previous commit.

Fixed several filtering bugs.

Several bugs with the acceleration filters cauased crashes and
incorrect results. Redid the error analysis and found some mistakes.
There was also a bug in the code for checking non-trivial intersections.
Now you can boolean a standard cube and cylinder and scale the cylinder
without crashing.
Also rewrote the tri-tri intersection code to make it more understandable
and also prepare the way for more floating filters.

Fix bugs re triangle sorting.

Several somewhat self-compensating bugs in the routine that sorts
triangles around an edge let to a bug visible with a unit cube
subtracting a unit cylinder with 4 sides. Fixed.

Fix building WITH_GMP in case of boolean modifier.

Left out a define.
Also, added more debugging in boolean.cc.