Modified 'denoise_bilateral':\n1) check that image max value is not zero to avoid segmentation fault.\n2) initialize color_lut after sigma_range has been checked.
Deported variable initialization after the cdef block to allow verifications.
Moved image conversion after the verification of the max_value
Merge pull request #576 from alexis-mignon/master

Bugs in filter.denoise_biltateral.