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

host/linktest/main.c

Index: host/linktest/main.c
diff --git a/host/linktest/main.c b/host/linktest/main.c
index 5fb7dd3d80b98779c5b973cf921f0dc2e36d9526..93c5ac2a9fdfcd8663ef1a42d22b0b2132af0251 100644
--- a/host/linktest/main.c
+++ b/host/linktest/main.c
@@ -1,6 +1,8 @@
 #include <stdio.h>
 
 #include "host_common.h"
+#include "file_keys.h"
+#include "signature_digest.h"
 
 int main(void)
 {
@@ -32,5 +34,16 @@ int main(void)
   CreateFirmwarePreamble(0, 0, 0, 0);
   CreateKernelPreamble(0, 0, 0, 0, 0, 0, 0);
 
+  /* file_keys.h */
+  BufferFromFile(0, 0);
+  RSAPublicKeyFromFile(0);
+  DigestFile(0, 0);
+  SignatureFile(0, 0, 0);
+
+  /* signature_digest.h */
+  PrependDigestInfo(0, 0);
+  SignatureDigest(0, 0, 0);
+  SignatureBuf(0, 0, 0, 0);
+
   return 0;
 }