Print message to stderr when EXIV2_DEBUG_MESSAGES is enabled.

src/crwimage_int.cpp

@@ -1236,6 +1236,10 @@ namespace Exiv2 {
             if (s <= size) {
                 if (len < s) len = s;
                 exif.copy(buf.pData_ + exif.tag() * 2, byteOrder);
+            } else {
+#ifdef EXIV2_DEBUG_MESSAGES
+                std::cerr << "packIfdId out-of-bounds error: s = " << std::dec << s << "\n";
+#endif
             }
         }
         // Round the size to make it even.