accommodate gnulib header removals

accommodate gnulib header removals

* src/copy.c: Don't include "euidaccess.h" or "lchmod.h".
* src/cp.c: Don't include "lchmod.h".
* src/ls.c: Don't include "dirfd.h".
* src/mkdir.c: Don't include "lchmod.h".
* src/pwd.c: Don't include "dirfd.h".
* src/remove.c: Don't include "dirfd.h" or "euidaccess.h".
* src/test.c: Don't include "euidaccess.h".
* gl/modules/getloadavg.diff: Adjust diff for changed context.
* src/uptime.c (uptime): Remove declaration.