Add SSL_CTX_get_ciphers.

This is an API from OpenSSL 1.1.0 which is a little risky to add ahead
of bumping OPENSSL_VERSION_NUMBER, but anything which currently builds
against BoringSSL already had an #ifdef due to the
ssl_cipher_preference_list_st business anyway.

Bump BORINGSSL_API_VERSION to make it easier to patch envoy for this.

BUG=6

Change-Id: If8307e30eb069bbd7dc4b8447b6e48e83899d584
Reviewed-on: https://boringssl-review.googlesource.com/14067
Reviewed-by: Steven Valdez <svaldez@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
diff --git a/include/openssl/ssl.h b/include/openssl/ssl.h
index 2d72fec..6b39096 100644
--- a/include/openssl/ssl.h
+++ b/include/openssl/ssl.h
@@ -1366,6 +1366,10 @@
  * inputs, unless an empty cipher list results. */
 OPENSSL_EXPORT int SSL_set_cipher_list(SSL *ssl, const char *str);
 
+/* SSL_CTX_get_ciphers returns the cipher list for |ctx|, in order of
+ * preference. */
+OPENSSL_EXPORT STACK_OF(SSL_CIPHER) *SSL_CTX_get_ciphers(const SSL_CTX *ctx);
+
 /* SSL_get_ciphers returns the cipher list for |ssl|, in order of preference. */
 OPENSSL_EXPORT STACK_OF(SSL_CIPHER) *SSL_get_ciphers(const SSL *ssl);