include/exec: Move tb hash functions out

include/exec: Move tb hash functions out

This is one of very few things in exec-all with a genuine CPU
architecture dependency. Move these hashing helpers to a new
header to trim exec-all.h down to a near architecture-agnostic
header.

The defs are only used by cpu-exec and translate-all which are both
arch-obj's so the new tb-hash.h has no core code usage.

Reviewed-by: Richard Henderson <[email protected]>
Signed-off-by: Peter Crosthwaite <[email protected]>
Message-Id: <9d048b96f7cfa64a4d9c0b88e0dd2877fac51d41.1433052532[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>