BoringSSL build issue

[Lukas Tribus]

> https://boringssl.googlesource.com/boringssl
>
> They didn't release yet so I just cloned the repo !

Sorry, I was thinking about libressl instead.

BoringSSL removed SSL_R_BLOCK_CIPHER_PAD_IS_WRONG return
errors in commits 1e52ecac4d and 29b186736c, and the definition was
finally removed in commit 689be0f4b7, which is what breaks the build
here.

You can workaround this by &ifdef'ing the line in ngx_event_openssl.c
out, nothing bad will happen because of this.

Not sure if it still makes sense to workaround every single build breakage
caused by upstream boringssl changes in nginx, seems like a never
ending cat and mouse game.


Lukas