Doxygen adjustment, and better directory name for GCryptLib

GCryptLib/include/Halfblock.h

@@ -0,0 +1,9 @@
+#pragma once
+#include "SecureBitset.h"
+#include <cstdint>
+#include "Config.h"
+
+namespace Leonetienne::GCrypt {
+  constexpr std::size_t HALFBLOCK_SIZE = (BLOCK_SIZE / 2);
+  typedef SecureBitset<HALFBLOCK_SIZE> Halfblock;
+}