If you allocate with wmem, free with wmem (more of same).

Change-Id: I10991dcb717a38936e2b7cf2f15885b5753378d0
Reviewed-on: https://code.wireshark.org/review/15034
Reviewed-by: Guy Harris <guy@alum.mit.edu>

epan/addr_resolv.c

@@ -2217,7 +2217,7 @@ read_subnets_file (const char *subnetspath)
 
         subnet_entry_set(host_addr, (guint32)mask_length, cp);
     }
-    g_free(line);
+    wmem_free(wmem_epan_scope(), line);
 
     fclose(hf);
     return TRUE;