Take Cryptographic API outside the XXX_ALT check

The cryptographic API should not be related to whether or not
there is alternative implementation. The API should be same for regular
implementation, and for alternative implementation, so it is defined
outside of the XXX_ALT precompilation check in the cryptographic API header

include/mbedtls/des.h

@@ -46,14 +46,14 @@
 
 #define MBEDTLS_DES_KEY_SIZE    8
 
-#if !defined(MBEDTLS_DES_ALT)
-// Regular implementation
-//
-
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#if !defined(MBEDTLS_DES_ALT)
+// Regular implementation
+//
+
 /**
  * \brief          DES context structure
  *
@@ -67,6 +67,10 @@ typedef struct
 }
 mbedtls_des_context;
 
+#else  /* MBEDTLS_DES_ALT */
+#include "des_alt.h"
+#endif /* MBEDTLS_DES_ALT */
+
 /**
  * \brief          Triple-DES context structure
  */
@@ -331,17 +335,6 @@ int mbedtls_des3_crypt_cbc( mbedtls_des3_context *ctx,
  */
 void mbedtls_des_setkey( uint32_t SK[32],
                          const unsigned char key[MBEDTLS_DES_KEY_SIZE] );
-#ifdef __cplusplus
-}
-#endif
-
-#else  /* MBEDTLS_DES_ALT */
-#include "des_alt.h"
-#endif /* MBEDTLS_DES_ALT */
-
-#ifdef __cplusplus
-extern "C" {
-#endif
 
 /**
  * \brief          Checkup routine