Add skeleton ecdsa.[ch]
diff --git a/library/ecdh.c b/library/ecdh.c
index 1515899..1b4fcd3 100644
--- a/library/ecdh.c
+++ b/library/ecdh.c
@@ -31,7 +31,7 @@
 
 #include "polarssl/config.h"
 
-#if defined(POLARSSL_ECP_C)
+#if defined(POLARSSL_ECDH_C)
 
 #include "polarssl/ecdh.h"
 
@@ -87,4 +87,4 @@
 
 #endif
 
-#endif /* defined(POLARSSL_ECP_C) */
+#endif /* defined(POLARSSL_ECDH_C) */