This avoids the detour over [gs]et_higher_type().

After a SubSP the top end of the stack is used and not just unused
alignment padding anymore.

Only the backends know how memperm are implementd and whether they use
sp- or fp-relative addressing. This should fix sparc memperm problems.

Long-term I'd like to remove the memperm node and use a callback that
creates a sequence of target specific nodes instead (similar to how
spills and reloads are created).

This is a bigger rewrite of stack frame handling in the backend:

- Do the stack frame type layout late, after all the spill slots have
  been created. This way we can avoid (and remove) the brittle
  frame_alloc_area().
- Standardize the meaning of stack entity offsets. After stack frame type
  layout they are relative to the stack pointer position at the beginning
  of the function.  It is all in one type now, no splitting into "arg",
  "between" and "stack_frame" type anymore.
- Generalize the stack pointer simulation code to work with a single
  callback. Represent stack state as current offset and align_padding
  number. Now that callbacks can access and modify them both we do not
  need custom code in the sparc backend anymore.
- Remove alignment specification on IncSP, only keep a ignore_align flag
  used for the last IncSP that has to remove all existing sp adjustments
  and may end up on a misaligned SP on ia32/amd64.
- Align stack by default on ia32+amd64 backends.

They previously used be_stack_layout but that structure will be remove
soon.

This fixes backend/sparc_stackframe.

Add callbacks on functions that really need them instead.

- It was only available in the ia32 backend and broken there. As the
  feature is rarely used, I remove it for now instead of going through
  the trouble of fixing it.

Types need not be in their final form after the new_entity so there is no
need to have _d variants like we have with all the graph nodes. You can easily
use set_entity_dbg_info() after construction.

This fix is necessary to avoid an assert in the new
itfield/compound_member code.

It has been empty for nearly all systems. People who used to put stuff
in config.h can still create a config.h on their own and inject
-include (gcc) or /FI (msvc) into their CPPFLAGS.

Just state the copyright and the project the files belong to. You can
then find the COPYING file for the whole project.