Revamp digest functions

- Hash() has been removed because it was ambiguous, Md5() and Sha0() are proper replacements.
- HMacMd5() and HMacSha1() now share a common implementation handled by the new Internal_HMac() function.
- NewMd() and MdProcess() now support plain hashing (without the key).
- NewMd(), SetMdKey() and MdProcess() now check the OpenSSL functions' return value and in case of failure a debug message is printed along with the error string, if available.
- SetMdKey()'s return value has been changed from void to bool, so that it's possible to know whether the function succeeded or not.
- MdProcess()' return value has been changed from void to UINT (unsigned int) and the function now returns the number of bytes written by HMAC_Final() or EVP_DigestFinal_ex().

src/Cedar/Nat.c

@@ -1193,7 +1193,7 @@ void NiAdminThread(THREAD *thread, void *param)
 					{
 						UCHAR test[SHA1_SIZE];
 						// Password match
-						Hash(test, "", 0, true);
+						Sha0(test, "", 0);
 						SecurePassword(test, test, random);
 
 #if	0
@@ -1793,7 +1793,7 @@ NAT *NiNewNatEx(SNAT *snat, VH_OPTION *o)
 	NAT *n = ZeroMalloc(sizeof(NAT));
 
 	n->lock = NewLock();
-	Hash(n->HashedPassword, "", 0, true);
+	Sha0(n->HashedPassword, "", 0);
 	n->HaltEvent = NewEvent();
 
 	//n->Cedar = NewCedar(NULL, NULL);