Add skeleton ecdh.[ch]
diff --git a/include/polarssl/ecp.h b/include/polarssl/ecp.h
index 6c52f96..e1b0995 100644
--- a/include/polarssl/ecp.h
+++ b/include/polarssl/ecp.h
@@ -27,7 +27,7 @@
 #ifndef POLARSSL_ECP_H
 #define POLARSSL_ECP_H
 
-#include "bignum.h"
+#include "polarssl/bignum.h"
 
 /*
  * ECP error codes