Use const for input mpz_t argument to pss_verify_mgf1.

ChangeLog

 2017-04-04  Niels Möller  <nisse@lysator.liu.se>
 
+	* pss.c (pss_verify_mgf1): Use const for input mpz_t argument.
+
 	Merged RSA-PSS support, contributed by Daiki Ueno.
 	* pss-mgf1.h, pss.h: New header files.
 	* pss-mgf1.c (pss_mgf1): New file and function.

pss.c

@@ -120,7 +120,7 @@ pss_encode_mgf1(mpz_t m, size_t bits,
  * Returns 1 if the encoded message is consistent, 0 if it is
  * inconsistent.  */
 int
-pss_verify_mgf1(mpz_t m, size_t bits,
+pss_verify_mgf1(const mpz_t m, size_t bits,
 		const struct nettle_hash *hash,
 		size_t salt_length,
 		const uint8_t *digest)

pss.h

@@ -53,7 +53,7 @@ pss_encode_mgf1(mpz_t m, size_t bits,
 		const uint8_t *digest);
 
 int
-pss_verify_mgf1(mpz_t m, size_t bits,
+pss_verify_mgf1(const mpz_t m, size_t bits,
 		const struct nettle_hash *hash,
 		size_t salt_length,
 		const uint8_t *digest);