Merge branch 'PR/libmount-vfs' of https://github.com/karelzak/util-linux-work

* 'PR/libmount-vfs' of https://github.com/karelzak/util-linux-work:
  docs: add VFS symbols to libmount-sections.txt
  tests: add libmount VFS test
  libmount: add VFS test to test_mount_context
  libmount: add pluggable VFS I/O support

diff --cc libmount/docs/libmount-sections.txt
Simple merge

diff --cc libmount/src/libmount.h.in
Simple merge

diff --cc libmount/src/mountP.h
Simple merge

diff --cc libmount/src/tab_parse.c
Simple merge