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/Protocol.c

@@ -873,7 +873,7 @@ void GenerateMachineUniqueHash(void *data)
 	WriteBuf(b, osinfo->OsVendorName, StrLen(osinfo->OsVendorName));
 	WriteBuf(b, osinfo->OsVersion, StrLen(osinfo->OsVersion));
 
-	Hash(data, b->Buf, b->Size, true);
+	Sha0(data, b->Buf, b->Size);
 
 	FreeBuf(b);
 }