Adapt sources to configurable config.h name
diff --git a/library/padlock.c b/library/padlock.c
index 6e94532..52b04f0 100644
--- a/library/padlock.c
+++ b/library/padlock.c
@@ -29,7 +29,11 @@
  *  programming_guide.pdf
  */
 
+#if !defined(POLARSSL_CONFIG_FILE)
 #include "polarssl/config.h"
+#else
+#include POLARSSL_CONFIG_FILE
+#endif
 
 #if defined(POLARSSL_PADLOCK_C)