Simply always set the registers of all outputs of the new Add.

The comment, stating that ia32_finish_irg_walker() starts more walks, is stale.
Therefore it is not necessary to first collect all nodes with a walker and then apply ia32_finish_irg_walker().

This fixes opt/fehler315.c

This fixes backend/chordal3.c.

This fixes backend/sparc_stackframe.

This fixes x86code/fehler132.c.

In particular, reduce the array size of the out_infos
instead of setting the flags register to NULL.

Size of last_uses has been increased and code is clear without the
comment anyway.

This reverts commit ccc99db0.

Without the assert it is easy to run into suble bugs because
be_get_backend_param() was called before all arguments are set by
be_parse_arg().

This fixes opt/fehler314.c.

This fixes backend/long_double_arith.c.

This fixes backend/chordal2.c.

This fixes opt/boolopt3.c.