feature-rbtree-test-impr:

* RB-tree test remove first was added;
* RB-tree test remove last was added.
Merge branch 'feature-rbtree-test-impr'
Feature timer:
 - Timer implementation was added;
 - Events now support timeouts;
 - Event test was updated.

Refactoring:
 - KF_ERR_EVBISY was renamed to KF_ERR_BUSY;
 - kfiber_event_alloc was renamed to alloc_event;
 - kfiber_root_coro_init was renamed to kfiber_coro_thread_init;
 - kfiber_after_fork was renamed to kfiber_thread_init.
 - kfiber_init was renamed to fiber_init;
Tests:
  - Timer module test was added.
Merge branch 'feature-timer'