cleanup library and some basic tests. Includes, add guards to includes
diff --git a/library/error.c b/library/error.c
index a4e6fc3..1be54e8 100644
--- a/library/error.c
+++ b/library/error.c
@@ -28,10 +28,13 @@
 
 #if defined(POLARSSL_ERROR_C) || defined(POLARSSL_ERROR_STRERROR_DUMMY)
 #include "polarssl/error.h"
+#include <string.h>
 #endif
 
 #if defined(POLARSSL_ERROR_C)
 
+#include <stdio.h>
+
 #if defined(POLARSSL_AES_C)
 #include "polarssl/aes.h"
 #endif
@@ -172,9 +175,6 @@
 #include "polarssl/xtea.h"
 #endif
 
-#include <stdio.h>
-#include <string.h>
-
 #if defined(_MSC_VER) && !defined  snprintf && !defined(EFIX64) && \
     !defined(EFI32)
 #define  snprintf  _snprintf
@@ -746,8 +746,6 @@
 
 #if defined(POLARSSL_ERROR_STRERROR_DUMMY)
 
-#include <string.h>
-
 /*
  * Provide an non-function in case POLARSSL_ERROR_C is not defined
  */