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

It should only be used by construction algorithms

public functions are already documented in their headers, no need to
repeat the comment at the definition site.

Define them in your own project if you must use them.

They were inconsistent with DEBUG_libfirm and unused

- Put things into logical groups
- Add cross references from node overview to API docu

They're pointless with the new switch representation introduced a while
ago.