Remove the CRYPTO_EX_new callback.

This callback is never used. The one caller I've ever seen is in Android
code which isn't built with BoringSSL and it was a no-op.

It also doesn't actually make much sense. A callback cannot reasonably
assume that it sees every, say, SSL_CTX created because the index may be
registered after the first SSL_CTX is created. Nor is there any point in
an EX_DATA consumer in one file knowing about an SSL_CTX created in
completely unrelated code.

Replace all the pointers with a typedef to int*. This will ensure code
which passes NULL or 0 continues to compile while breaking code which
passes an actual function.

This simplifies some object creation functions which now needn't worry
about CRYPTO_new_ex_data failing. (Also avoids bouncing on the lock, but
it's taking a read lock, so this doesn't really matter.)

BUG=391192

Change-Id: I02893883c6fa8693682075b7b130aa538a0a1437
Reviewed-on: https://boringssl-review.googlesource.com/6625
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/ssl/ssl_session.c b/ssl/ssl_session.c
index ead0b75..0dcfdd8 100644
--- a/ssl/ssl_session.c
+++ b/ssl/ssl_session.c
@@ -172,7 +172,7 @@
   session->references = 1;
   session->timeout = SSL_DEFAULT_SESSION_TIMEOUT;
   session->time = (unsigned long)time(NULL);
-  CRYPTO_new_ex_data(&g_ex_data_class, session, &session->ex_data);
+  CRYPTO_new_ex_data(&session->ex_data);
   return session;
 }
 
@@ -278,12 +278,13 @@
   return SSL_SESSION_up_ref(ssl->session);
 }
 
-int SSL_SESSION_get_ex_new_index(long argl, void *argp, CRYPTO_EX_new *new_func,
+int SSL_SESSION_get_ex_new_index(long argl, void *argp,
+                                 CRYPTO_EX_unused *unused,
                                  CRYPTO_EX_dup *dup_func,
                                  CRYPTO_EX_free *free_func) {
   int index;
-  if (!CRYPTO_get_ex_new_index(&g_ex_data_class, &index, argl, argp, new_func,
-                               dup_func, free_func)) {
+  if (!CRYPTO_get_ex_new_index(&g_ex_data_class, &index, argl, argp, dup_func,
+                               free_func)) {
     return -1;
   }
   return index;