packetize Phong shader
new scons config options:
simd=(yes|no) - allow/suppress explicit SSE
force_flags=(yes|no) - force use of specified flags instead of autodetected
profile=(yes|no) - enable gcc's profiling (-pg option)
check for pthread.h header, don't try to build without it
add fourth Vector3 component for better memory aligning
rename Vector3 to Vector
partialy SSE-ize Vector class (only fully vertical operations)
build static lib and python module in distinctive directories
to avoid collision of library file names on some platforms