Move SHA256 class to libroot instead of linking libshared into libroot.

Discussed with PulkoMandy and on the haiku-commits mailing list.

Thanks to @jessicah for compile-testing and fixing 2 small issues I missed.

headers/private/libroot/SHA256.h

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2008, Ingo Weinhold, [email protected].
+ * Distributed under the terms of the MIT License.
+ */
+#ifndef _SHA_256_H
+#define _SHA_256_H
+
+
+#include <SupportDefs.h>
+
+
+#define SHA_DIGEST_LENGTH	32
+
+namespace BPrivate {
+
+
+class SHA256 {
+public:
+								SHA256();
+								~SHA256();
+
+			void				Init();
+			void				Update(const void* buffer, size_t size);
+			const uint8*		Digest();
+			size_t				DigestLength() const
+									{ return SHA_DIGEST_LENGTH; }
+
+private:
+			void				_ProcessChunk();
+
+private:
+			uint32				fHash[8];
+			uint32				fDigest[8];
+			uint32				fBuffer[64];
+			size_t				fBytesInBuffer;
+			size_t				fMessageSize;
+			bool				fDigested;
+};
+
+
+} // namespace BPrivate
+
+using BPrivate::SHA256;
+
+
+#endif	// _SHA_256_H