The panic function might allocate memory via ir_vfprintf, so we must
not use it in the out of memory case.  Otherwise we get an infinite loop.

Improvements:
- added support for -march=atom
- fixed some assignments of incompatible enum types
- simplified code

This also plugs liveness related memory leaks

Types "own" entities, so they should also free them when they get freed.

It was a member of ir_prog before but not correctly handled.

The first block in a new ir_graph is not an immature block anymore. The
end block is matured in irg_finalize_cons() now (since maturing blocks
twice doesn't hurt this shouldn't break existing code).

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().

unknown_type, code_type, none_type, unknown_entity reference are hold in
the irprog now. This makes handling more consistent since now all types
and entities are equally part of irprog.

Now every bit in the public API is documented so we can enable doxygen
warnings for undocumented members.

They are really special cases for obstack_printf, we don't need them for
all of libfirm.

Replace with equivalent pset_ptr stuff