(Cosmetic) kt_shadow_clear is dead code and seems broken

[kimgr]

kt_shadow_clear appears to be getting the end of the shadow region wrong:

void kt_shadow_clear(uptr_t addr, size_t size)
{
	void *shadow_beg;
	void *shadow_end;
	size_t shadow_size;

	shadow_beg = kt_shadow_get(addr);
	shadow_end = kt_shadow_get(addr);

I'm guessing it should say something like shadow_end = shadow_begin + size; or shadow_end = kt_shadow_get(addr + size); instead. But in either case it's never called, so maybe just scrap it?

[dvyukov]

Hi @kimgr,

I guess we need to drop it if it's unused.
This code is currently on hold, we will take care of this when we revive work on KTSAN.

Thanks