Remove unused ex_data indexes.

The unused ex_data index declarations are commented out instead of
removed so that it is clear which values to avoid for any new ex_data
indexes added in the future.

Change-Id: Ia19da9631324492c5c7eeacc71453e6240c73870
Reviewed-on: https://boringssl-review.googlesource.com/3940
Reviewed-by: Adam Langley <agl@google.com>

include/openssl/ex_data.h

@@ -213,22 +213,19 @@ OPENSSL_EXPORT void *CRYPTO_get_ex_data(const CRYPTO_EX_DATA *ad, int index);
  * User defined classes start at 100.
  *
  * TODO(fork): WARNING: these are called "INDEX", but they aren't! */
-#define CRYPTO_EX_INDEX_BIO 0
-#define CRYPTO_EX_INDEX_SSL 1
-#define CRYPTO_EX_INDEX_SSL_CTX 2
-#define CRYPTO_EX_INDEX_SSL_SESSION 3
-#define CRYPTO_EX_INDEX_X509_STORE 4
-#define CRYPTO_EX_INDEX_X509_STORE_CTX 5
-#define CRYPTO_EX_INDEX_RSA 6
-#define CRYPTO_EX_INDEX_DSA 7
-#define CRYPTO_EX_INDEX_DH 8
-#define CRYPTO_EX_INDEX_ENGINE 9
-#define CRYPTO_EX_INDEX_X509 10
-#define CRYPTO_EX_INDEX_UI 11
-#define CRYPTO_EX_INDEX_EC_KEY 12
-#define CRYPTO_EX_INDEX_EC_GROUP 13
-#define CRYPTO_EX_INDEX_COMP 14
-#define CRYPTO_EX_INDEX_STORE 15
+enum {
+  CRYPTO_EX_INDEX_BIO,
+  CRYPTO_EX_INDEX_SSL,
+  CRYPTO_EX_INDEX_SSL_CTX,
+  CRYPTO_EX_INDEX_SSL_SESSION,
+  CRYPTO_EX_INDEX_X509_STORE,
+  CRYPTO_EX_INDEX_X509_STORE_CTX,
+  CRYPTO_EX_INDEX_RSA,
+  CRYPTO_EX_INDEX_DSA,
+  CRYPTO_EX_INDEX_DH,
+  CRYPTO_EX_INDEX_X509,
+  CRYPTO_EX_INDEX_EC_KEY,
+};
 
 
 /* User-defined classes of objects.