[libpng17] Transformed rewrite: changed row_info, added checks. This introduces an

    internal struct (png_transform_control) to replace row_info and uses
    that to implement affirms correctly.  The change also adds checks on
    the rowbytes calculation and additional checks on most transform
    implementations.
Added png_uint_16 range checking, pngvalid tRNS, fixed png_uint_16:
    review of previous checks, removal of some where SAFE. pngvalid: add
    testing of tRNS for better code coverage pngvalid: correct rgb-to-gray
    error calculations. Code coverage is still incomplete: see /*UNTESTED*/
    in pngrtran.c
14 files changed