Avoid using restartable and alternative ECP imp.
1. Add a check that MBEDTLS_ECP_RESTARTABLE is not defined
along any EC* alternative implementation.
2. Add a closing comment foran `#endif`.
diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index 28e860b..c594b69 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -694,6 +694,9 @@
* for too long on ECC (and, hence, X.509 or SSL/TLS) operations.
*
* Uncomment this macro to enable restartable ECC computations.
+ *
+ * \note MBEDTLS_ECP_RESTARTABLE cannot be defined if there is an alternative
+ * implementation for one of the ECP, ECDSA or ECDH functions. *
*/
//#define MBEDTLS_ECP_RESTARTABLE