Draft Parallel Linear BVH Broadphase.
Use merged AABB to calculate grid cell size for PLBVH.
Fix PLBVH reduction kernels, simplify nodes per level calculation.

Also calculate index ranges for each internal node.
Accelerate GPU raycaster with PLBVH.
Various minor PLBVH related changes.

-Use most significant bit instead of negative for internal nodes.
-Explicitly store root node index, so that it does not have to be 0.
-Check the root node first in PLBVH traversal.
-Fix rigid body clipping in RaytracedShadowDemo.
Fix PLBVH with 0/1 nodes, fix optimized ray-AABB intersect.
Split PLBVH files into .h/.cpp.

Also move PLBVH binary tree construction into separate function.
Add only small AABBs to PLBVH, add large AABB support.
Draft PLBVH construction using binary radix tree.
Merge various commits into a single commit.

Commits after:
2014-03-03 Draft PLBVH construction using binary radix tree.
f19f85368517ff08a4f329710a1710f547c545d2

Are merged into a single commit; this includes:
03-10 Remove single launch build AABB kernel.
03-10 Add kernels for setting PLBVH AABBs using distance from root.
03-10 Use faster morton code, remove convertChildNodeFormat kernel.
03-09 Add duplicate morton code handling to binary radix construct.
03-09 Remove slower PLBVH constructors.
03-08 Add binary radix tree construct using binary search.
03-06 Remove slowest PLBVH constructor, fix implicit construct AABB.
03-04 Test various optimizations for PLBVH binary radix tree construct.
Clean up PLBVH construction, add comments.
Fix PLBVH raycast when only 1 small AABB is added to the tree.
Add PLBVH documentation/slides.
Fix PLBVH symmetry optimization for calculateOverlappingPairs().
Add access to overlapping pairs b3OpenCLArray.
Clean up plbvhCalculateOverlappingPairs kernel.

Also fix overlapping pair generation with triangle mesh.
(Currently, large/concave AABBs must be the first entry in a pair.)
Add overlapping pairs validation to PairBench.
Avoid memory leak with validation broadphase in PairBench.
Merge pull request #160 from rtrius/plbvh_raycast

Plbvh raycast