Debug dlopen error

We're currently getting occasional segfaults when failing to dlopen
encoding files. The segfault is preventing us from seeing the raised
error message, so this printing will let us see it in the logs instead.

Author: composerinteralia

dln.c

@@ -429,6 +429,7 @@ dln_open(const char *file)
     return handle;
 
   failed:
+    fprintf(stderr, "DLOPEN ERROR: %s - %s\n", error, file);
     dln_loaderror("%s - %s", error, file);
 }