Merge branch 'rename-interactive' of https://github.com/g-raud/util-linux

Merge branch 'rename-interactive' of https://github.com/g-raud/util-linux

* 'rename-interactive' of https://github.com/g-raud/util-linux:
  rename: fixup & style (no functional changes)
  rename: test availability of __fpurge() and fpurge()
  rename: ask(): call __fpurge() to cater for multi-byte characters
  rename.1: describe interactive mode
  rename: ask(): print n when EOF on input
  rename: detect tty in cbreak mode to make ask() read a single byte
  rename.1: fix warning section
  rename: add option --interactive to ask before overwriting
  rename: skip faccessat() failure if AT_SYMLINK_NOFOLLOW is not a valid flag
  rename: check source file access early