The callee/caller saved information is not constant accross different
ABI's, so don't make it constant. Instead, all BE that still use beabi
provide a callback now.
This allows to implement support for x64_64/Win32 and is a necessary step
for the combined x86 BE.

[r28172]

remove strange init_once/inited checks from arch_init functions. Calling it twice is invalid (and crashs anyway)

[r28152]

[r28127]

[r28070]

[r28068]

[r28062]

[r28039]

[r28038]

[r28037]

[r28033]

[r28028]

[r28010]

eliminate the unnecessary and especially confusing concept of a 'code_generator' an isa-interface is enough

[r28009]

[r28002]

[r28001]

[r28000]

[r27995]

allow backend to specify endianess, rewrite bitfield emitter to handle little and big-endian byte order

[r27974]

[r27973]

[r27972]

[r27957]

[r27956]