Add some MACROS LIKE LL_REVERSE() to support reverse the list

[govc]

Please Add some macros to support reverse the list.
`
struct item{
int id;
struct item*next;
};

struct itemhead = NULL;
void additem(int id)
{
struct itemi = malloc(sizeof(*i));
i->id = id;
LL_PREPEND(head, i);
}

void add()
{
for(int i=0; i<1000000; i++)
additem(i);
}

int main(){
add();
LL_REVERSE(head);
return 0;
}

`

[Quuxplusone]

Closing as a duplicate of #197. I'm still amenable to such an addition; I just haven't had time or inclination to work on it specifically. Patches are still welcome.