cleanup library and some basic tests. Includes, add guards to includes

library/bignum.c

@@ -38,16 +38,18 @@
 #include "polarssl/bignum.h"
 #include "polarssl/bn_mul.h"
 
+#include <string.h>
+
 #if defined(POLARSSL_PLATFORM_C)
 #include "polarssl/platform.h"
 #else
+#include <stdio.h>
+#include <stdlib.h>
 #define polarssl_printf     printf
 #define polarssl_malloc     malloc
 #define polarssl_free       free
 #endif
 
-#include <stdlib.h>
-
 /* Implementation that should never be optimized out by the compiler */
 static void polarssl_zeroize( void *v, size_t n ) {
     volatile unsigned char *p = v; while( n-- ) *p++ = 0;