Modified pmapcontrib modules to PRESERVE the coarsest level wavelet approximation coefficients. Tests showed that these should NOT be thresholded, nor mRGBE encoded as this introduces unacceptable compression artefacts. The approximations are now saved to the coefficient file as 32-bit RGBE before the mRGBE encoded details. In support of this, and for improved clarity, convencience macros WAVELET_PADD4_APPROXDIM, WAVELET_PADD4_NUMAPPROX and WAVELET_PADD4_NUMDETAIL were added to wavelet2.h. PMAP_CONTRIB_ENCSIZE() in pmapcontrib.h was also updated accordingly. For improved efficiency, thresholdContribs() now only sorts NONZERO detail coefficients.