Use the same work-around for the memdebug stuff as in the command line client,

to allow the contents of the env var decide the file name.

tests/libtest/first.c

@@ -19,8 +19,14 @@ int main(int argc, char **argv)
   /* this sends all memory debug messages to a logfile named memdump */
   char *env = curl_getenv("CURL_MEMDEBUG");
   if(env) {
+    /* use the value as file name */
+    char *s = strdup(env);
     curl_free(env);
-    curl_memdebug("memdump");
+    curl_memdebug(s);
+    free(s);
+    /* this weird strdup() and stuff here is to make the curl_free() get
+       called before the memdebug() as otherwise the memdebug tracing will
+       with tracing a free() without an alloc! */
   }
   /* this enables the fail-on-alloc-number-N functionality */
   env = curl_getenv("CURL_MEMLIMIT");