[libpng16] Make all three "make check" test programs work without READ or WRITE

support.  Now "make check" will succeed even if libpng is compiled with
-DPNG_NO_READ or -DPNG_NO_WRITE.  The tests performed are reduced, but the
basic reading and writing of a PNG file is always tested by one or more of
the tests.
diff --git a/CHANGES b/CHANGES
index 2f91295..1da41ea 100644
--- a/CHANGES
+++ b/CHANGES
@@ -4184,6 +4184,10 @@
     for compressed text chunks).
   Consistently use png_memset(), png_memcpy(), and png_memcmp(), except in
     pngtest.c and example.c where these macros are not visible.
+  Make all three "make check" test programs work without READ or WRITE support.
+    Now "make check" will succeed even if libpng is compiled with -DPNG_NO_READ
+    or -DPNG_NO_WRITE.  The tests performed are reduced, but the basic reading
+    and writing of a PNG file is always tested by one or more of the tests.
 
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