Infer it from block.

That way the spill engine can rematerialize the loads and needs no
extra spills for these values.

The only user knwos, where its sp is.

some inputs had "no requirement" set instead of the correct one

(It was set to NULL in the past to support the STA-architecture, but
 that backend is not maintained anymore)

Remove now redundant (and sometimes wrong) location info from the panic messages.

Get away from the strange set_default_XXX_op style and instead let the
code modules register their node ops directly.

The opcode list was a member of irprog before which wasn't really
handled consistently. Also make sure opcodes are properly freed at
ir_finish().

memops are nodes that have memory inputs, you can generically query them
for their memory input. We can also get rid of get_fragile_op_mem in
favor of get_memop_mem.

So we are not forced to use the generic be_Spill, be_Reload functions
which don't work correctly with double-width register requirements.
This should really fix sparc float spill/reload this time.

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)