lib: llist: Fixed setting (after)->next->prev in DLLIST2_INSERT_AFTER_FULL. This function was not yet used, so the problem did not affect existing code.

lib: DLLIST*_REMOVE*() no longer breaks the linked list if we try to remove item that doesn't exist there. Hopefully there wasn't any code that actually did this, but it's safer this way anyway. Perhaps it could be even made to assert-crash if it happens.

liblib: Added DLLIST2_INSERT_AFTER_FULL() For inserting a new element in a doubly-linked list after an existing element.

liblib: Added _FULL versions of all linked list handling macros with prev and next params. This allows putting structs into multiple linked lists.

Added DLLIST2_*() functions for doubly linked list with head and tail. --HG-- branch : HEAD

DLLIST_REMOVE(): Set removed item's prev/next pointers to NULL. --HG-- branch : HEAD

Added macros for handling a doubly linked list. --HG-- branch : HEAD