#2 id3_lookup_frame lookes for more then 4 chars

[dan stavy]

This causes equal tags to return as non equal
here is the fix:

id3_lookup_frame(id3v2_frame_list *list, const char *field, const int pos)
{
int cur = 0;

if(!list || !field) return NULL;

do
{
if(!strncmp(list->data->frame_id, field,4)) // this is the FIX
{
if(cur == pos) return list->data;
cur++;
}
} while((list = list->next));

return NULL;
}