Add dummy |SSL_COMP_free_compression_methods|.

cURL calls this function if |OPENSSL_VERSION_NUMBER| is in [0x10002003,
0x10002fff], which it now is for BoringSSL after 0aecbcf6.

Change-Id: I3f224f73f46791bd2232a1a96ed926c32740a6f6
Reviewed-on: https://boringssl-review.googlesource.com/11461
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>

include/openssl/ssl.h

@@ -3153,6 +3153,9 @@ OPENSSL_EXPORT int SSL_COMP_add_compression_method(int id, COMP_METHOD *cm);
 /* SSL_COMP_get_name returns NULL. */
 OPENSSL_EXPORT const char *SSL_COMP_get_name(const COMP_METHOD *comp);
 
+/* SSL_COMP_free_compression_methods does nothing. */
+OPENSSL_EXPORT void SSL_COMP_free_compression_methods(void);
+
 /* SSLv23_method calls |TLS_method|. */
 OPENSSL_EXPORT const SSL_METHOD *SSLv23_method(void);
 

ssl/ssl_cipher.c

@@ -1996,6 +1996,8 @@ int SSL_COMP_add_compression_method(int id, COMP_METHOD *cm) { return 1; }
 
 const char *SSL_COMP_get_name(const COMP_METHOD *comp) { return NULL; }
 
+void SSL_COMP_free_compression_methods(void) {}
+
 int ssl_cipher_get_key_type(const SSL_CIPHER *cipher) {
   uint32_t alg_a = cipher->algorithm_auth;