small percentage for 16-bit and 32-bit pixels in the typical case where the
output row buffers are appropriately aligned. The optimization was not
previously possible because the png_struct buffer was always misaligned.

caused by a bug in the code that attempted to align it; the code needs to
subtract one from the pointer to take account of the filter byte prepended to
each row.

generality of the code, allowing it to be optimized for Adam7 interlace.  The
masks passed to png_combine_row() are now generated internally, avoiding
some code duplication and localizing the interlace handling somewhat.

not supported.

with a loop.

from CMakeLists.txt that is no longer useful in libpng-1.5.

Added "--strict" option to pngtest, to report FAIL when the failure is
only because the resulting valid files are different.

macro.

called only once with a particular info_ptr.

The 16-bit cases still use "L" as we don't have a 16-bit test system.

to conditions where types that are 32 bits in the GCC 32-bit
world (uLong and png_size_t) become 64 bits in the 64-bit
world.  This produces potential truncation errors which the
compiler correctly flags.

png_XYZ_from_xy_checked

by default.