Remove unused files, and tidy the directory structure of the remaining ones.

host/include/signature_digest.h

 /* Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef VBOOT_REFERENCE_SIGNATURE_DIGEST_H_
 #define VBOOT_REFERENCE_SIGNATURE_DIGEST_H_
 
 #include <inttypes.h>
 
 /* Returns a buffer with DigestInfo (which depends on [algorithm])
  * prepended to [digest].
  */
-uint8_t* prepend_digestinfo(int algorithm, uint8_t* digest);
+uint8_t* PrependDigestInfo(int algorithm, uint8_t* digest);
 
 /* Function that outputs the message digest of the contents of a buffer in a
  * format that can be used as input to OpenSSL for an RSA signature.
  * Needed until the stable OpenSSL release supports SHA-256/512 digests for
  * RSA signatures.
  *
  * Returns DigestInfo || Digest where DigestInfo is the OID depending on the
  * choice of the hash algorithm (see padding.c). Caller owns the returned
  * pointer and must Free() it.
  */
 uint8_t* SignatureDigest(const uint8_t* buf, uint64_t len, int algorithm);
 
 /* Calculates the signature on a buffer [buf] of length [len] using
  * the private RSA key file from [key_file] and signature algorithm
  * [algorithm].
  *
  * Returns the signature. Caller owns the buffer and must Free() it.
  */
 uint8_t* SignatureBuf(const uint8_t* buf, uint64_t len, const char* key_file,
                       int algorithm);
 #endif  /* VBOOT_REFERENCE_SIGNATURE_DIGEST_H_ */