Merge branch 'lslocks--co-holders' of https://github.com/masatake/util-linux

* 'lslocks--co-holders' of https://github.com/masatake/util-linux:
  tests: (lslocks) add cases testing HOLDERS column
  tests: (cosmetic,lslocks) trim whitespaces at the end of line
  tests: (test_mkfds::make-regular-file) add a new parameter, "dupfd"
  lslocks: add HOLDERS column
  lslocks: store list_add_tail when storing information extracted from /proc/$pid/fdinfo/$fd
  tests: (test_mkfds) initialize a proper union member
  xalloc.h: add new functions: xstrappend, xstrputc, xstrvfappend, and xstrfappend
  lsfd: (refactor) make the code comparing struct lock objects reusable
  lslocks: add a missing "break;" in a switch/case statement
  lslocks: (preparation) add a fd number to the lock struct when loading lock info from /proc/$pid/fdinfo/$fd
  lslocks: (refactor) use a tree for storing lock information extracted from /proc/$pid/fdinfo/$fd
  lslocks: (refactor) make the data structure for storing lock information replacable