libpng-1.5.19beta03 and 1.6.11beta03 are available from
ftp://ftp.simplesystems.org/pub/png-group/src
and from
http://libpng.sf.net

Version 1.5.19beta03 [April 6, 2014]
  Removed #if/#else/#endif from inside two pow() calls in pngvalid.c because
    they were handled improperly by Portland Group's PGI-14.1 - PGI-14.3
    when using its "__builtin_pow()" function.
  Silence 'unused parameter' build warnings (Cosmin).
  $(CP) is now used alongside $(RM_F).  Also, use 'copy' instead
    of 'cp' where applicable, and applied other minor makefile changes.
  Don't warn about invalid dimensions exceeding user limits.
  Allow an easy replacement of the default pre-built configuration
    header with a custom header, via the make PNGLIBCONF_H_PREBUILT
    macro.
  Fixed a typo in pngrutil.c, introduced in libpng-1.5.6, that interferes
    with "blocky" expansion of sub-8-bit interlaced PNG files (Eric Huss).

Version 1.6.11beta03 [April 6, 2014]
  Fixed a typo in pngrutil.c, introduced in libpng-1.5.6, that interferes
    with "blocky" expansion of sub-8-bit interlaced PNG files (Eric Huss).