pngcp: tool to copy PNG files

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: John Bowler <jbowler@acm.org>

Makefile.am

@@ -13,7 +13,7 @@ check_PROGRAMS += timepng
 endif
 
 # Utilities - installed
-bin_PROGRAMS= pngfix png-fix-itxt
+bin_PROGRAMS= pngcp pngfix png-fix-itxt
 
 # This ensures that pnglibconf.h gets built at the start of 'make all' or
 # 'make check', but it does not add dependencies to the individual programs,
@@ -48,6 +48,9 @@ png_fix_itxt_SOURCES = contrib/tools/png-fix-itxt.c
 timepng_SOURCES = contrib/libtests/timepng.c
 timepng_LDADD = libpng@PNGLIB_MAJOR@@PNGLIB_MINOR@.la
 
+pngcp_SOURCES = contrib/tools/pngcp.c
+pngcp_LDADD = libpng@PNGLIB_MAJOR@@PNGLIB_MINOR@.la
+
 # Generally these are single line shell scripts to run a test with a particular
 # set of parameters:
 TESTS =\
@@ -231,6 +234,7 @@ contrib/libtests/timepng.o: pnglibconf.h
 
 contrib/tools/makesRGB.o: pnglibconf.h
 contrib/tools/pngfix.o: pnglibconf.h
+contrib/tools/pngcp.o: pnglibconf.h
 
 # We must use -DPNG_NO_USE_READ_MACROS here even when the library may actually
 # be built with PNG_USE_READ_MACROS; this prevents the read macros from