Constify d2i, s2i, c2i and r2i functions and other associated
functions and macros.

This change has associated tags: LEVITTE_before_const and
LEVITTE_after_const.  Those will be removed when this change has been
properly reviewed.
diff --git a/crypto/evp/p_open.c b/crypto/evp/p_open.c
index bc39408..8ec6c75 100644
--- a/crypto/evp/p_open.c
+++ b/crypto/evp/p_open.c
@@ -65,8 +65,9 @@
 #include <openssl/objects.h>
 #include <openssl/x509.h>
 
-int EVP_OpenInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type, unsigned char *ek,
-	     int ekl, unsigned char *iv, EVP_PKEY *priv)
+int EVP_OpenInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
+	const unsigned char *ek, int ekl, const unsigned char *iv,
+	EVP_PKEY *priv)
 	{
 	unsigned char *key=NULL;
 	int i,size=0,ret=0;