Added code to set photon contribs from a set of reference contribs obtained from rcontrib classic (included from rc-ref.c) to check whether deviations under real world conditions are due to photon contributions or the encoding. These contribs can also be enabled in the padded wavelet xform unit test. It turns out these contribs can result in NEGATIVE approximation coefficients in the upper left of the wavelet matrix, presumably due to boundary extension. The coefficients are currently erroneously clamped to 0 when encoded as 32-bit RGBE in encodeContribs()!!!