Begin adding MJPEGTOOLS_SIMD_DISABLE environment variable support. The environ
variable is a comma separated list of routine names that should use the C code
instead of the SIMD (MMX/SSE/Altivec) code. At the present time only the
support function, the helper program (mjpeg_simd_helper) and 1 of the motion
routine checks has been completed. The remainder (and the quantization/dct
rountes) will be done as time permits.
