Add exit value macros to platform abstraction layer.
diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index d9b37e0..c9332e1 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -131,7 +131,7 @@
 //#define MBEDTLS_PLATFORM_NO_STD_FUNCTIONS
 
 /**
- * \def MBEDTLS_PLATFORM_EXIT_ALT
+ * \def MBEDTLS_PLATFORM_XXX_ALT
  *
  * MBEDTLS_PLATFORM_XXX_ALT: Uncomment a macro to let mbed TLS support the
  * function in the platform abstraction layer.
@@ -2469,6 +2469,8 @@
 //#define MBEDTLS_PLATFORM_STD_PRINTF        printf /**< Default printf to use, can be undefined */
 /* Note: your snprintf must correclty zero-terminate the buffer! */
 //#define MBEDTLS_PLATFORM_STD_SNPRINTF    snprintf /**< Default snprintf to use, can be undefined */
+//#define MBEDTLS_PLATFORM_STD_EXIT_SUCCESS       0 /**< Default exit value to use, can be undefined */
+//#define MBEDTLS_PLATFORM_STD_EXIT_FAILURE       1 /**< Default exit value to use, can be undefined */
 
 /* To Use Function Macros MBEDTLS_PLATFORM_C must be enabled */
 /* MBEDTLS_PLATFORM_XXX_MACRO and MBEDTLS_PLATFORM_XXX_ALT cannot both be defined */