external/boringssl: Sync to 54c259dec395bd991cce5691723214ffe588e51d.

This includes the following changes:

https://boringssl.googlesource.com/boringssl/+log/8459d0659920ab8c99bd300b8a989d4cda251118..54c259dec395bd991cce5691723214ffe588e51d

Test: BoringSSL CTS Presubmits.
Change-Id: I1868f252e94e424d450ebd8983549d9b13455613
diff --git a/src/include/openssl/mem.h b/src/include/openssl/mem.h
index 92cbb0d..6c21512 100644
--- a/src/include/openssl/mem.h
+++ b/src/include/openssl/mem.h
@@ -69,20 +69,28 @@
 
 // Memory and string functions, see also buf.h.
 //
-// OpenSSL has, historically, had a complex set of malloc debugging options.
-// However, that was written in a time before Valgrind and ASAN. Since we now
-// have those tools, the OpenSSL allocation functions are simply macros around
-// the standard memory functions.
+// BoringSSL has its own set of allocation functions, which keep track of
+// allocation lengths and zero them out before freeing. All memory returned by
+// BoringSSL API calls must therefore generally be freed using |OPENSSL_free|
+// unless stated otherwise.
 
 
-#define OPENSSL_malloc malloc
-#define OPENSSL_realloc realloc
-#define OPENSSL_free free
+// OPENSSL_malloc acts like a regular |malloc|.
+OPENSSL_EXPORT void *OPENSSL_malloc(size_t size);
 
-// OPENSSL_realloc_clean acts like |realloc|, but clears the previous memory
-// buffer.  Because this is implemented as a wrapper around |malloc|, it needs
-// to be given the size of the buffer pointed to by |ptr|.
-void *OPENSSL_realloc_clean(void *ptr, size_t old_size, size_t new_size);
+// OPENSSL_free does nothing if |ptr| is NULL. Otherwise it zeros out the
+// memory allocated at |ptr| and frees it.
+OPENSSL_EXPORT void OPENSSL_free(void *ptr);
+
+// OPENSSL_realloc returns a pointer to a buffer of |new_size| bytes that
+// contains the contents of |ptr|. Unlike |realloc|, a new buffer is always
+// allocated and the data at |ptr| is always wiped and freed.
+OPENSSL_EXPORT void *OPENSSL_realloc(void *ptr, size_t new_size);
+
+// OPENSSL_realloc_clean behaves exactly like |OPENSSL_realloc|.
+// TODO(martinkr): Remove.
+OPENSSL_EXPORT void *OPENSSL_realloc_clean(void *ptr, size_t old_size,
+                                           size_t new_size);
 
 // OPENSSL_cleanse zeros out |len| bytes of memory at |ptr|. This is similar to
 // |memset_s| from C11.