libxc: split xc_logdirty_control() from xc_shadow_control()

libxc: split xc_logdirty_control() from xc_shadow_control()

For log-dirty operations a 64-bit field is being truncated to become an
"int" return value. Seeing the large number of arguments the present
function takes, reduce its set of parameters to that needed for all
operations not involving the log-dirty bitmap, while introducing a new
wrapper for the log-dirty bitmap operations. This new function in turn
doesn't need an "mb" parameter, but has a 64-bit return type. (Using the
return value in favor of a pointer-type parameter is left as is, to
disturb callers as little as possible.)

While altering xc_shadow_control() anyway, also adjust the types of the
last two of the remaining parameters.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Acked-by: Ian Jackson <iwj@xenproject.org>