(They are passed in integer registers, so we can immediately create
integer constants)

This is the new way of handling switch-jumps. The node contains a table
which maps (ranges of) input values to proj numbers. Compared to a
Cond-node this results in a clean consecutive sequence of Proj numbers
(no searching for a free number for the default_pn anymore) and allows
factoring multiple cases jumping to the same block in a single Proj
(though we still need the optimisation in cfopt for that).

(see testsuite/backend/sparc_notconsts.c for an example)

This was an odd convention from the past, there's no need for it
anymore.

- Make API private as it should only be called by backends
- Let ia32 backend create special ia32_Set nodes instead of relying
  on muxes which must not be touched anymore
- Does not create ConvB nodes anymore but instead produces the Cmp
  directly. (All backends did this anyway during code-selection so I was
  able to leave this case out code-selection)
- First collect nodes to lower, then lower them. This avoids robustness
  problems when transforming the graph while at the same time walking
  it.

This should also fix compound returns in combination with
-msoft-float on sparc

(Hannes ancient technique based on the Proj-mode is deprecated)

This commit also adds a generic Alloc/Free lowering helper
Unfortunately we often produce invalid code, because currently our
stackpointer wiring logic is too weak and produces invalid results for
example when using alloca in a loop.

This tries to get the names in a consistent format. We basically have 2
views on register allocation/constraints now:

1) Register Requirements and Assigments are per-instruction. Each
   instruction has requirements on its inputs and outputs, register get
   assigned for outputs of an instruction (assignment is an attribute of
   an instruction, not of the Proj-nodes).
   The internal datastructures model this form!

   The functions here have the form:
     arch_get_irn_register_req_in(node, input_nr)
     arch_get_irn_register_in(node, input_nr)
     arch_get_irn_register_req_out(node, output_nr)
     arch_set_irn_register_out(node, output_nr, register)

2) Register Requirements and Assignments are on firm-values. This view
   allows to query/assign requirements and registers at the Proj nodes
   instead of the repsective predecessors.
   This is a convenience interface modeled on top of the other!

   The functions have the form:
     arch_get_irn_register_req(node)
     arch_get_irn_register(node)
     arch_set_irn_register(node, register)

Since we have no complicated barrier/prolog stuff in the transform phase
anymore we can move away from beabihelper now and create the nodes
directly which will be necessary when modeling special constraints like
wide aligned registers.

So sparc can handle this case now.

Use a special kind of entity on the frame type instead of a value_type
struct inside a method type. This makes replacement of function types
slightly easier (it's still a complex operation though) and handling in
the backend a bit more consistent since it's more or less a normal stack
access (with special offsets).