Merge branch 'master' into core-updates

system: Tell module-init-tools where to look for modules.

* gnu/packages/linux.scm (module-init-tools)[source](patches): New
  field.
* gnu/packages/patches/module-init-tools-moduledir.patch: New file.
* gnu-system.am (dist_patch_DATA): Add it.
* gnu/system.scm (etc-directory): Add #:kernel parameter.  Set
  'LINUX_MODULE_DIRECTORY' in bashrc.
  (operating-system-etc-directory): Pass #:kernel to 'etc-directory'.