set ABI to 4.slh.1.

* set ABI to 4.slh.1.
* merge overlayfs from v3.18-rc5+:
  - ovl-rename-filesystem-type-to-overlay
  - ovl-fix-remove-copy-up-race
  - ovl-fix-race-in-private-xattr-checks
  - ovl-allow-filenames-with-comma
  - ovl-use-lockless_dereference-for-upperdentry
  - ovl-pass-dentry-into-ovl_dir_read_merged
  - ovl-update-MAINTAINERS
  - ovl-ovl_dir_fsync-cleanup
* import 3.17.4.
* import 3.17.4-rc1.
NOT RELEASED YET

* NOT RELEASED YET
* set ABI to 4.slh.2.