hw: remove deprecated TLB declaration

fix #1320
base: for-each method for FIFOs

ref #1102
hw: rename Thread::State SCHEDULED in ACTIVE

As soon as helping is used, a thread may also be in a blocking state when its
scheduling context is ready. Hence, the state designation SCHEDULED for an active
thread would be pretty misleading.

ref #1102
hw: helping on IPC

On base-hw, each thread owns exactly one scheduling context for its
whole lifetime. However, introducing helping on IPC, a thread might get
executed on scheduling contexts that it doesn't own. Figuratively
spoken, the IPC-helping relation spans trees between threads. These
trees are identical to those of the IPC relation between threads. The
root of such a tree is executed on all scheduling contexts in the tree.
All other threads in the tree are not executed on any scheduling context
as long as they remain in this position. Consequently, the ready-state
of all scheduling contexts in an IPC-helping tree always equals the
state of the root context.

fix #1102