Testing commit
Fixed bug where cones would be missing 1 or more faces
in ScenePrimitive::TYPE_CONE / Mesh::createCone.
--
Observed when creating cone with params:
(height 3.5, radius 2.0, numSegments 12)

Occurred as original algorithm assumes that lastx > -1 for all iteratiosn
except first pass of vertex calculation.  lastx instead has lower bound of
-1*radius of cone, so will often be <= -1 when radius is 1 or greater.
In my test examples, I sometimes needed to rotate the cone->setYaw(90) to
observe that the faces were missing.