target: Include softmmu_exec.h where forgotten

Several targets forgot to include softmmu_exec.h, which would
break them with a header cleanup to follow.

Signed-off-by: Richard Henderson <rth@twiddle.net>
exec: Split softmmu_defs.h

The _cmmu helpers can be moved to exec-all.h.  The helpers that are
used from TCG will shortly need access to tcg_target_long so move
their declarations into tcg.h.

This requires minor include adjustments to all TCG backends.

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg: Introduce zero and sign-extended versions of load helpers

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-i386: Perform tail call to qemu_ret_ld*_mmu

This does require the fast path always load to the function return
value register, but apparently the loaded value usually needs to be
spilled back to its memory slot anyway so the change in register
does not really change much.

Signed-off-by: Richard Henderson <rth@twiddle.net>