Log Message:
Version 1.7.52 (built with libpng-1.6.1beta06 and zlib-1.2.7)
  Added license info for cexcept.h, libpng, and zlib.
  Added consideration of "zopfli" compression to the "To do" \ 
list.
  Fixed a typo that caused a cHRM chunk to be "found" if an iCCP chunk
    were present.
  Reset best_byte_count before trial loop.
  Revise global png_set_keep_unknown_chunks() calls to avoid a libpng16
    warning.
  Reset "intent" to "specified_intent" before trial loop.
  Reset "plte_len" to "specified_plte_len" before trial loop.
  Initialize length of each trial to 0x7fffffff so any untried method
    is not the "best method".