Remove app_data from EVP_PKEY_CTX.

It's never used. It's not clear why one would want such a thing.
EVP_PKEY_CTX has no way for callers to register callbacks, which means
there shouldn't be a way for the library to present you an EVP_PKEY_CTX
out-of-context. (Whereas app_data/ex_data makes sense on SSL because of
its numerous callbacks or RSA because of RSA_METHOD.)

Change-Id: I55af537ab101682677af34f6ac1f2c27b5899a89
Reviewed-on: https://boringssl-review.googlesource.com/6849
Reviewed-by: Adam Langley <alangley@gmail.com>

crypto/evp/evp_ctx.c

@@ -193,12 +193,6 @@ err:
 
 EVP_PKEY *EVP_PKEY_CTX_get0_pkey(EVP_PKEY_CTX *ctx) { return ctx->pkey; }
 
-void EVP_PKEY_CTX_set_app_data(EVP_PKEY_CTX *ctx, void *data) {
-  ctx->app_data = data;
-}
-
-void *EVP_PKEY_CTX_get_app_data(EVP_PKEY_CTX *ctx) { return ctx->app_data; }
-
 int EVP_PKEY_CTX_ctrl(EVP_PKEY_CTX *ctx, int keytype, int optype, int cmd,
                       int p1, void *p2) {
   if (!ctx || !ctx->pmeth || !ctx->pmeth->ctrl) {

crypto/evp/internal.h

@@ -218,8 +218,6 @@ struct evp_pkey_ctx_st {
   int operation;
   /* Algorithm specific data */
   void *data;
-  /* Application specific data */
-  void *app_data;
 } /* EVP_PKEY_CTX */;
 
 struct evp_pkey_method_st {

include/openssl/evp.h

@@ -428,14 +428,6 @@ OPENSSL_EXPORT EVP_PKEY_CTX *EVP_PKEY_CTX_dup(EVP_PKEY_CTX *ctx);
 /* EVP_PKEY_CTX_get0_pkey returns the |EVP_PKEY| associated with |ctx|. */
 OPENSSL_EXPORT EVP_PKEY *EVP_PKEY_CTX_get0_pkey(EVP_PKEY_CTX *ctx);
 
-/* EVP_PKEY_CTX_set_app_data sets an opaque pointer on |ctx|. */
-OPENSSL_EXPORT void EVP_PKEY_CTX_set_app_data(EVP_PKEY_CTX *ctx, void *data);
-
-/* EVP_PKEY_CTX_get_app_data returns the opaque pointer from |ctx| that was
- * previously set with |EVP_PKEY_CTX_set_app_data|, or NULL if none has been
- * set. */
-OPENSSL_EXPORT void *EVP_PKEY_CTX_get_app_data(EVP_PKEY_CTX *ctx);
-
 /* EVP_PKEY_sign_init initialises an |EVP_PKEY_CTX| for a signing operation. It
  * should be called before |EVP_PKEY_sign|.
  *