and always use png_calloc().  The macros were only there for testing,
since libpng-1.4.0beta48 and no problems have been reported.

Always use local arrays, which has been the default behavior
for a long time.

They were only useful for obtaining compatibility for old applications
that used libpng-1.0.x versions prior to the implementation of "free_me".

except in pngconf.h where they can be used to request that
PNG_FEATURE_SUPPORTED not be defined.

in png.c (suggested by Peter Breitenlohner)

to see if that works better for the auto-license-detectors