Runtime check when the default relative alignment is overridden, needs to be added.

[sulekhark]

Given below is a scenario (adapted and reduced from musl's memchr conversion to checkedc) where a runtime check (as per section 3.9.2 of the spec) needs to be added:

$ cat relalign.c
void test (const void *src : itype(_Array_ptr<const void>) byte_count(arg_n), unsigned int arg_n)
_Checked
{
        unsigned int n = arg_n;
        _Array_ptr<const unsigned char> s : bounds((_Array_ptr<const unsigned char>)src,
                                                   (_Array_ptr<const unsigned char>)src + arg_n)
                                          = (_Array_ptr<const unsigned char>) src;
        for (;  *s; s++, n--);
        if (n && *s) {
                _Array_ptr<unsigned int> w : bounds((_Array_ptr<const unsigned char>)src,
                                                    (_Array_ptr<const unsigned char>)src + arg_n) rel_align(unsigned char)
                                           = 0;
                for (w = (_Array_ptr<void>)s; n>=4 && *w; w++, n-=4);
        }
}

[sulekhark]

This issue is covered by #329. Closing it.