See http://www.libfirm.org/Unreachable_Code for details

add unknown_jump opflag for the special case of a jump where we can't directly influence the destination and can't predict/change them

This avoids a Load without ProjM, instead of handling this case.

Reverts the previous commit.

A Load might not have a ProjM

The associated link combinaes onbe lowered awith one unlowered type,
it cannot be used for chains of unlowered types.

Removes the get_type_[un]lowered() API and restores the
get_associated_type() API.

However, the whole concept of lowered types should be replaced by type
attributes ...

This fixes the asserts in stabs debug output.

Fixed the "naive and wrong regex stubs", so it has the right signature and returns the right value/error code now.

Simplify: if (!irn_visited(x)) { mark_irn_visited(x); ... }  ->  if (!irn_visited_else_mark(x)) { ... }.

This is asserted in the next statement anyways

* get_associated_type is unnecessary
* is_lowered_type is an internal inline function now
* set_lowered_type is an internal inline function now

This fixes opt/jumpthreading3.c.

* removed unnecessary call_tp variable
* removed shadowed tp variable (twice)

Similiar to 9d207c0 the call lowering should always use the current
entity type, instead of the associate type, which may or may not be
a lowered type.