Expose the CTR_DRBG API.

Change-Id: Ie071dcd94d2ae8aa8ee148682f9b0054ed9e3501
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/52445
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
diff --git a/include/openssl/base.h b/include/openssl/base.h
index b74e66f..76955c7 100644
--- a/include/openssl/base.h
+++ b/include/openssl/base.h
@@ -389,6 +389,7 @@
 typedef struct conf_value_st CONF_VALUE;
 typedef struct crypto_buffer_pool_st CRYPTO_BUFFER_POOL;
 typedef struct crypto_buffer_st CRYPTO_BUFFER;
+typedef struct ctr_drbg_state_st CTR_DRBG_STATE;
 typedef struct dh_st DH;
 typedef struct dsa_st DSA;
 typedef struct ec_group_st EC_GROUP;