Make CTR mode behaviour consistent with other modes:

clear ctx->num in EVP_CipherInit_ex

Submitted by: Emilia Kasper

crypto/evp/evp.h

@@ -419,7 +419,7 @@ struct evp_cipher_ctx_st
 	unsigned char  oiv[EVP_MAX_IV_LENGTH];	/* original iv */
 	unsigned char  iv[EVP_MAX_IV_LENGTH];	/* working iv */
 	unsigned char buf[EVP_MAX_BLOCK_LENGTH];/* saved partial block */
-	int num;				/* used by cfb/ofb mode */
+	int num;				/* used by cfb/ofb/ctr mode */
 
 	void *app_data;		/* application stuff */
 	int key_len;		/* May change for variable length cipher */

crypto/evp/evp_enc.c

@@ -232,6 +232,7 @@ skip_to_init:
 			break;
 
 			case EVP_CIPH_CTR_MODE:
+			ctx->num = 0;
 			/* Don't reuse IV for CTR mode */
 			if(iv)
 				memcpy(ctx->iv, iv, EVP_CIPHER_CTX_iv_length(ctx));