Adapt sources to configurable config.h name
diff --git a/library/aesni.c b/library/aesni.c
index e396d43..9d21c85 100644
--- a/library/aesni.c
+++ b/library/aesni.c
@@ -28,7 +28,11 @@
  * [CLMUL-WP] http://software.intel.com/en-us/articles/intel-carry-less-multiplication-instruction-and-its-usage-for-computing-the-gcm-mode/
  */
 
+#if !defined(POLARSSL_CONFIG_FILE)
 #include "polarssl/config.h"
+#else
+#include POLARSSL_CONFIG_FILE
+#endif
 
 #if defined(POLARSSL_AESNI_C)