basic: add LIST_INSERT_BEFORE Similar in function to LIST_INSERT_AFTER, this will insert a new element into the list before the specified position. If the specified position is NULL, the element is added as the tail of the list.

test: duplicate LIST_FOREACH_OTHERS test to check for corner cases of end and start of list

list: add macro for iterating through a list an item is in, skipping the item

shared/list: add LIST_APPEND

list: make our list macros a bit easier to use by not requring type spec on each invocation We can determine the list entry type via the typeof() gcc construct, and so we should to make the macros much shorter to use.

test: Add list testcase