gnu: guile-static: Add bindings for `reboot'.

* gnu/packages/patches/guile-linux-syscalls.patch: Add `scm_reboot'.

gnu: guile-static: Add bindings for low-level Linux syscalls.

* gnu/packages/make-bootstrap.scm (%guile-static): Add
  `guile-linux-syscalls.patch' as an input, and use it.
* gnu/packages/patches/guile-linux-syscalls.patch: New file.
* Makefile.am (dist_patch_DATA): Add it.