utmpx.h is no longer under standards, so expose ut_exit structure
utmpx.h is no longer under standards, so expose ut_exit structure

chneukirchen/musl-chris2,chardi/musl,rofl0r/musl-old,rofl0r/musl-old,davidlazar/musl,chardi/musl,chneukirchen/musl-chris2,chardi/musl,davidlazar/musl