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Especially, do not confirm consistent out edges.
This fixes ack/t7.c on SPARC.

Apparently it is optional on linux (just often used because the RIP
encoding is often shorter than a global encoding).

Along the way:
- Simplified code to sharpen Cmp relations
- Do not remove unreachable code by using bit information anymore

This fixes opt/fehler230.c.

compute() does this check already before calling compute_Phi().

IJmp supplies its successors with reachability information.
It is not necessary to force all labeled blocks to reachable.

"Es ist Deutschland hier" so we use the european style interpretation of
top/bottom.

This commit does:
- Remove tarval_reachable+tarval_unreachable, dataflow analysis rather
  use top/bottom instead of other special values.
- Rename tarval_undefined to tarval_unknown as it corresponds to the
  Unknown node (=a value which we don't know)
- Remove predefined tarval_top/tarval_bottom from tv.h and place the
  defines into combo.c
- Change compute_XXX constant folding functions to return tarval_unknown
  instead of tarval_bad if folding failed
- compute_Unknown in combo results in tarval_bottom == tarval_unknown
  this eliminates strange special cases in the Cond/Switch rules and the
  now unnecessary cprop_X list.

Optimizing arithmetic with Unknown nodes to a new Unknown node is
illegal unless you can prove that the original Unknown node has no
other users.

We previously used NoMem as dependency for the stores of parameters
whose address is taken. This was wrong as obviously other code inside
the inlined function may change the value which might make a dependency
necessary in case of loops.

This fixes firm-testsuite/opt/fehler228.c

This fixes opt/combo8.c.

Now mode_b behaves the same as integer modes, so use the same code to initialize the special values.

The removed special case used the same color anyway.