This finally removes the last Android hack. Both Chromium and Android
end up needing this thing (Chromium needs it for WebCrypto but currently
uses the EVP_AEAD version and Android needs it by way of
wpa_supplicant).

On the Android side, the alternative is we finish upstream's
NEED_INTERNAL_AES_WRAP patch, but then it just uses its own key-wrap
implementation. This seems a little silly, considering we have a version
of key-wrap under a different API anyway.

It also doesn't make much sense to leave the EVP_AEAD API around if we
don't want people to use it and Chromium's the only consumer. Remove it
and I'll switch Chromium to the new---er, old--- APIs next roll.

Change-Id: I23a89cda25bddb6ac1033e4cd408165f393d1e6c
Reviewed-on: https://boringssl-review.googlesource.com/11410
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>