Restore |ERR_print_errors()|.

Change-Id: If289c4aa2804727d6c5e8386b5a2b559cf006415
Reviewed-on: https://boringssl-review.googlesource.com/5152
Reviewed-by: Adam Langley <agl@google.com>

include/openssl/bio.h

diff --git a/include/openssl/bio.h b/include/openssl/bio.h
index a1ab699..1843f4e 100644
--- a/include/openssl/bio.h
+++ b/include/openssl/bio.h
@@ -685,6 +685,12 @@
                                                     size_t bytes_written);
 
 
+/* Deprecated functions. */
+
+/* ERR_print_errors is an alias for |BIO_print_errors|. */
+OPENSSL_EXPORT void ERR_print_errors(BIO *bio);
+
+
 /* BIO_NOCLOSE and |BIO_CLOSE| can be used as symbolic arguments when a "close
  * flag" is passed to a BIO function. */
 #define BIO_NOCLOSE 0