Adapt sources to configurable config.h name
diff --git a/library/ecdh.c b/library/ecdh.c
index e35602d..fa32593 100644
--- a/library/ecdh.c
+++ b/library/ecdh.c
@@ -30,7 +30,11 @@
  * RFC 4492
  */
 
+#if !defined(POLARSSL_CONFIG_FILE)
 #include "polarssl/config.h"
+#else
+#include POLARSSL_CONFIG_FILE
+#endif
 
 #if defined(POLARSSL_ECDH_C)