add MSVC compiler support, make it default for Windows
new header file simd.h for SSE abstraction and helpers
  add mselect pseudo instruction for common or(and(...), andnot(...))
  replace many SSE intrinsics with new names
new MemoryPool class (mempool.h) for faster KdNode allocation
remove setMaxDepth() from Octree and KdTree, make max_depth const,
  it should be defined in constructor and never changed, change after
  building tree would cause error in traversal
modify DefaultSampler to generate nice 2x2 packets of samples for packet tracing
optimize Box and BBox::intersect_packet
add precomputed invdir attribute to RayPacket
scons build system:
  check for pthread library on Windows
  check for SDL
  generate include/config.h with variables detected by scons configuration
  move auxiliary files to build/
  add sanity checks
add writable operator[] to Vector
Import('env')
myenv = Environment()
myenv.Append(BUILDERS = {'Copy':Builder(action=Copy('$TARGET','$SOURCE'), single_source=True)})
files = ['lwo/Nissan300ZX.lwo', 'obj/cube.obj', 'obj/sphere.obj', 'obj/monkey.obj']
l = []
for file in files:
	l.append( myenv.Copy('#build/models/'+file, file) )
env.Alias('local-models', l)
plydir = Dir('#build/models/ply/')
import os
env.Command(plydir, [], '"'+Dir('#models/').abspath+os.sep+'download-stanford" $TARGET')
Clean(plydir, plydir)
env.Alias('download-models', plydir)
env.Alias('models', ['local-models', 'download-models'])