Remove const.lisp

const.lisp is not used now.
Use translator directly in field get/set

giargs and make-out does not help much in field get/set.  Remove its
usage, so that we can change their interface to fix the in-out and out
parameter support.
Fix in-out and out argument processing

After checking python gobject binding, found that in-out and out
parameters should pass by pointer even via g_function_info_invoke().
So fix in-out and out argument processing accordingly.
Merge pull request #7 from hying-caritas/fix-inout-out-arg

Fix inout and out arguments