Let's hope noone inserts new builtin kinds in the middle.

The length is now set on creation.
Neither length nor element type can be changed later on.

They are not used yet as we need an adapted layout algorithm for them.

This is done by introducing a new new_global_entity() function for
constructing globals/adding a visibility argument to new_alias_entity().

This is cleaner than having them being class types with a tf_segment
flag set.

The simple tp_opcode enum is enough, no need to have dispatch tables and
information structs behind each type kind.

Also choose a signed integer type which is more typical for offsets.

For stabs debug info it was used to suppress debug info, so set ir_visibility_private instead.

Avoid using the op_pin_state enum as that contains confusing additional
entries that are not valid on a node. The only remaining state for a
node is pinned/floating which we can simply represent with a 0/1 value.

This is not really a new entity type but merely a relocation type.
Handle it with a x86_immediate_kind.

Both functions do the same and the former is used way less.

This also renders get_irg_n_anchors() obsolete, so remove it.

* No \n at end; panic() adds one
* No punctuation mark at end
* Lowercase first letter

- 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.

- Compound type selection is performed with Member
- Array indexing is performed with Sel
- Instead of the simpleSel constructor functions you can use the normal Member
  constructors now
- The concept of array element entities has been removed, Sel nodes just
  contain a pointer to the array type now.