This flag can be set on entities where the actual address isn't
known/compared against other address. This also fixes a bug where we
used the mach-o csrings section for global char arrays which need
distinct addresses.

Default initialisation just happens to set the correct value.

mode_E is only 10 bytes wide but we should still use the 12byte wide
type_E for better alignment/consistency.

We can see that we need a frame entity if the the immediate has a
X86_IMM_FRAMEOFFSET relocation but no entity assigned yet.

Also move ir_nodemap struct into a new irnodemap_t.h file.

This resolves problems with hidden dependencies during code selection, which cause dependency cycles and therefore fixes backend/scheduled.c.
Also it grants the code selection slightly more freedom by not arbitrarily restricting the order by stack dependencies.

be: Pass the input requirements directly to the constructors of nodes, which have a variable number of arguments.