The extra free in ex_data_impl.c is fixing a mistake: when calling
|CRYPTO_cleanup_all_ex_data| the |EX_CLASS_ITEM| itself wouldn't be
freed.

The change in err_impl.c is to free the thread-id hash also. This allows
programs to free absolutely all memory allocated by BoringSSL, which
allows fuzz testing to find any memory leaks.

Change-Id: I1e518adf2b3e0efa7d7f00f7ab4e65e1dc70161e
Reviewed-on: https://boringssl-review.googlesource.com/2670
Reviewed-by: Adam Langley <agl@google.com>