[libpng16] Changed ICC profile support to allow use of an external color

management system (CMS). In practice it is not possible to obtain cHRM
information reliably using just the end-point tags because they do not exist
in the vast majority of profiles.  Instead it is necessary to run the endpoints
through the ICC colorimetric intent transform (as described in the v4
spec).  Since this is likely to be too much code inside libpng for too
little gain (it implies a fairly complete CMS implementation) the code
has been changed to allow an external CMS to be used.  This code is
temporarily disabled until a suitable set of test cases using one or more
external CMS implementations have been implemented.

pngerror.c

@@ -510,6 +510,41 @@ png_chunk_benign_error(png_const_structrp png_ptr, png_const_charp
 #endif
 #endif /* PNG_READ_SUPPORTED */
 
+void /* PRIVATE */
+png_chunk_report(png_const_structrp png_ptr, png_const_charp message, int error)
+{
+   /* This is always supported, but for just read or just write it
+    * unconditionally does the right thing.
+    */
+#  if (defined PNG_READ_SUPPORTED) && (defined PNG_WRITE_SUPPORTED)
+      if (png_ptr->mode & PNG_IS_READ_STRUCT)
+#  endif
+
+#  ifdef PNG_READ_SUPPORTED
+      {
+         if (error < PNG_CHUNK_ERROR)
+            png_chunk_warning(png_ptr, message);
+
+         else
+            png_chunk_benign_error(png_ptr, message);
+      }
+#  endif
+
+#  if (defined PNG_READ_SUPPORTED) && (defined PNG_WRITE_SUPPORTED)
+      else if (!(png_ptr->mode & PNG_IS_READ_STRUCT))
+#  endif
+
+#  ifdef PNG_WRITE_SUPPORTED
+      {
+         if (error < PNG_CHUNK_WRITE_ERROR)
+            png_app_warning(png_ptr, message);
+
+         else
+            png_app_error(png_ptr, message);
+      }
+#  endif
+}
+
 #ifdef PNG_ERROR_TEXT_SUPPORTED
 #ifdef PNG_FLOATING_POINT_SUPPORTED
 PNG_FUNCTION(void,