Math Lib: add isect_line_line_epsilon_v3
Fix filenames in splashscreen.

For some reason, labels of buttons in popups/menus were clipped left.

Removed that function (was the only place were it was used), clipping text
by its left is really bad for its understanding!

Instead, extended clip_middle code so that it optionnally preserves a right piece of
the given string (like the shortcut part of a menu label). Think that's what makes
more sense here (note that most menus adapt themselves to their longest item,
we do not have much fixed-width ones, anyway).

Also tweaked a bit clip_middle logic, so that left part always have at least ten chars
(in addition to already existing 'min width' checks).
Fix poll func of CYCLES_OT_use_shading_nodes.

Operators' poll func might be called from anywhere in Blender, so they should
not make any assumption about available context. material, lamp and world
are specific to context from Properties space...
Math Lib: replace epsilon with check against zero

line-tri intersection depended on scale, The check made small triangles & lines fail.
So just check for divide by zero as ray-cast currently does.
initial intersect code
initial isect
intersection script
test vert intersection
check for intersections where no new verts are added first
minor fixes
WIP
add vert-edge check
Print info
De-duplicate - dont add same verts to edge multiple times
Dissolve
Dissolve based on tags
improve intersection dissolve
Dissolve now works
WIP
WIP