Because png_handle_pCAL has allocated memory to free.
Signed-off-by: NJohn Bowler <jbowler@acm.org>

This adds pngcp to the build together with a pngcp.dfa configuration test; the
test revealed some configuration bugs which are fixed by corrections to the
_SUPPORTED macros.

pngcp builds on all tested configurations and a number of bugs have been fixed
to make this happen relative to the version in libpng 1.7 contrib/examples.
pngcp.dfa will have to be different for 1.7 but pngcp.c should work fine (not
yet tested).  pngcp itself is still missing a usage message; this is a
preliminary version, although since it behaves the same way as 'cp' most unoids
shouldn't have a problem using it correctly.
Signed-off-by: NJohn Bowler <jbowler@acm.org>

not info_ptr.

in png_set_cHRM_XYZ_fixed().

(Bug report by Viktor Szaka'ts).

tests/pngunknown-sAPI so it's temporarily marked SKIP.

pngset.c to avoid warnings about dead code.

values that are exactly 2^bit_depth, and work on 16-bit platforms.

in the code the number of elements in an array is calculated using
sizeof.  This generates a compile time constant of type (size_t) which
is then typically assigned to an (unsigned int) or (int). Some versions
of GCC on 64-bit systems warn about the apparent narrowing, even though
the same compiler does apparently generate the correct, in-range,
numeric constant.  This adds appropriate, safe, casts to make the
warnings go away.

"if (x !== 0)"