Fix the lack of isblank() with VMS C

#include <ctype.h>

#include <stdio.h>

/*

 * Even though the VMS C RTL claims to be C99 compatible, it's not entirely

 * so far (C RTL version 8.4).  For the sake of these tests, we therefore

 * define our own.

 */

#if defined(__VMS) && __CRTL_VER <= 80400000

static int isblank(int c)

{

    return c == ' ' || c == '\t';

}

#endif

static int test_ctype_chars(int n)

{

    return TEST_int_eq(isalnum(n) != 0, ossl_isalnum(n) != 0)