pkcs11-tool: various improvements, extensions, fixes, cleanup

========================================
rebased by VTA -- commits are forged to one,
excluding the following chunk
(reason -- if not explicitely indicated, the mechanism has to be found out using the mechanism flags):

@@ -1713,8 +1713,9 @@ static int gen_keypair(CK_SLOT_ID slot, CK_SESSION_HANDLE session,
                        int ii;

                        if (!opt_mechanism_used)
+                               opt_mechanism = CKM_EC_KEY_PAIR_GEN;
                                if (!find_mechanism(slot, CKF_GENERATE_KEY_PAIR, mtypes, mtypes_num, &opt_mechanism))
-                                       util_fatal("Generate EC key mechanism not supported\n");
+                                       util_warn("Generate EC key mechanism not listed as supported");

                        for (ii=0; ec_curve_infos[ii].name; ii++)   {
                                if (!strcmp(ec_curve_infos[ii].name, type + 3))

will close PR #747

src/pkcs11/pkcs11.h

@@ -657,6 +657,10 @@ typedef unsigned long ck_mechanism_type_t;
 #define CKM_EC_KEY_PAIR_GEN		(0x1040UL)
 #define CKM_ECDSA			(0x1041UL)
 #define CKM_ECDSA_SHA1			(0x1042UL)
+#define CKM_ECDSA_SHA224		(0x1043UL)
+#define CKM_ECDSA_SHA256		(0x1044UL)
+#define CKM_ECDSA_SHA384		(0x1045UL)
+#define CKM_ECDSA_SHA512		(0x1046UL)
 #define CKM_ECDH1_DERIVE		(0x1050UL)
 #define CKM_ECDH1_COFACTOR_DERIVE	(0x1051UL)
 #define CKM_ECMQV_DERIVE		(0x1052UL)