This also fixes a possible null pointer access.

Now register requirements always have have a register class.
This is more consistent and removes some null pointer checks.

We can easily identify the outputs producing a stack pointer by looking
if the stack pointer register is assigned. Unfortunately this also
needed a new mechanism to tell the verifier that some registers are not
in SSA form (all the time) which needs a few extra lines in each
backend.

be: Move the info about the register classes and registers struct the arch_env_t into struct arch_isa_if_t.

belive: Replace the union for head and nodes of the liveness sets by a struct with a flexible array member.

Projs are not scheduled anymore for a long time.

Add callbacks on functions that really need them instead.

Move the values interfere function to belive.h, move the inline
implementation into belive.c

- Remove value_dominates_intrablock()/value_strictly_dominates_intrablock()
  and use sched_comes_before() instead
- Use bool instead of int return types.
- Assert that we don't check if a node interferes with itself as that is
  nearly always a bug in the code.

As they were just a single flag the name should reflect that. I did not
change arch_irn_flags_none, as that is not about a single flag.

also removed some assert(0) used in verifiers to stop when compiling
with assertions (you better use your debugger to stop and keep the code
clean)

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.