Modified wavelet xform in pm*contrib*.c to always preserve the 3x3 approximation coeffs in the upper left of the coefficient matrix; these are now exempt from thresholding and stored as 32-bit RGBE; the corresponding photon's flux now contains the summed contributions. This substantially improves the reconstruction and minimises compression artefacts. Also added PMAP_MAXCONTRIBSRC_IDX to pmapdata.h to prevent overflowing PhotonContribSource.srcIdx.