Use inline functions rather than macros for cpu_ld/st accessors
for the *-user configurations, as we already do for softmmu.
This has a two advantages:
* we can actually typecheck our arguments
* we don't need to leak the _raw macros everywhere
Since the _kernel functions were only used by target-i386/seg_helper.c,
put the definitions for them in that file too. (It already has the
similar template include code to define them for the softmmu case,
so it makes sense to have it deal with defining them for user-only.)
Backports commit 9220fe54c679d145232a28df6255e166ebf91bab from qemu
