Remove superfluous const from CRYPTO_BUFFER_len.

Tagging non-pointer return types const doesn't do anything and makes
some compilers grumpy. Thanks to Daniel Hirche for the report.

Change-Id: I157ddefd8f7e604b4d8317ffa2caddb8f0dd89de
Reviewed-on: https://boringssl-review.googlesource.com/11849
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>

crypto/pool/pool.c

@@ -191,7 +191,7 @@ const uint8_t *CRYPTO_BUFFER_data(const CRYPTO_BUFFER *buf) {
   return buf->data;
 }
 
-const size_t CRYPTO_BUFFER_len(const CRYPTO_BUFFER *buf) {
+size_t CRYPTO_BUFFER_len(const CRYPTO_BUFFER *buf) {
   return buf->len;
 }
 

include/openssl/pool.h

@@ -62,7 +62,7 @@ OPENSSL_EXPORT const uint8_t *CRYPTO_BUFFER_data(const CRYPTO_BUFFER *buf);
 
 /* CRYPTO_BUFFER_len returns the length, in bytes, of the data contained in
  * |buf|. */
-OPENSSL_EXPORT const size_t CRYPTO_BUFFER_len(const CRYPTO_BUFFER *buf);
+OPENSSL_EXPORT size_t CRYPTO_BUFFER_len(const CRYPTO_BUFFER *buf);
 
 /* CRYPTO_BUFFER_init_CBS initialises |out| to point at the data from |buf|. */
 OPENSSL_EXPORT void CRYPTO_BUFFER_init_CBS(const CRYPTO_BUFFER *buf, CBS *out);