Include configuration file to headers

Add inclusion to configration file in header files,
instead of relying on other header files to include
the configuration file. This issue resolves #1371
diff --git a/include/mbedtls/padlock.h b/include/mbedtls/padlock.h
index 677936e..918e619 100644
--- a/include/mbedtls/padlock.h
+++ b/include/mbedtls/padlock.h
@@ -25,6 +25,12 @@
 #ifndef MBEDTLS_PADLOCK_H
 #define MBEDTLS_PADLOCK_H
 
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
 #include "aes.h"
 
 #define MBEDTLS_ERR_PADLOCK_DATA_MISALIGNED               -0x0030  /**< Input data should be aligned. */