- Only iterating over the graph once should be slightly faster
- We don't need to insert the middle of register allocation logic but
  can perform it once before.
- We can gather statistics on the prepared graph before spilling/regalloc has
  happened.

Note that for OO code you should use liboo which provides the same
features!

This allows the fronted to register a dump+verify callback for the
lowering transformations performed by the backends.

The new code has less options and variants, if you call irg_verify()
verification is performed, regardless of DEBUG_libfirm, or NDEBUG being
set and regardless of firm verification setting switches. On the other
side no atomic dump and abort is performed anymore, the call has to do
this, though an irg_assert_verify() function has been added as a
convenience measure.
There has also been a complete rewrite of the actual checking performed.
The new code is simpler, should produce more consistent output and
can report more than one error.

No need to do it in backend preparation phase, if some backends destroy
the property again before transformation.

- The backends can simply perform the finish_graph() steps in the emit()
  phase.

- You can now construct the lookup table separately and perform the
  lowering selectively on irgs (instead of the whole program at once)
  while reusing the lookup table.
- Simplified API a bit.
- Remove i_mapper_RuntimeCall. All users are simpler by doing the
  transformations directly instead of filling in runtime_rt
  structures...

before_abi() callback was removed, you can simply put that code at the end
of the init() callback. custom_abi flag was removed, if a backend needs the
be_abi_introduce() stuff (formerly custom_abi == false) then it can call
it at the end of the init() callback.

Nobody uses it currently, and it is a burden for everyone writing a new
pass.

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.

This especially removes unused complicated error reporting mechanisms

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

In particular this ensures that the backend has segments for the PIC symbols and trampolines.

bemain: Centrally call be_gas_end_compilation_unit() and be_emit_exit() instead of doing it per backend.

Also remove the now write-only attribute main_env from struct arch_env_t.

bemain: Centrally call be_emit_init() and be_gas_begin_compilation_unit() instead of doing it per backend.

It only measures initializing a single struct.

Remove empty init_graph functions from arm and sparc backends.