maint: prefer 'file system' over 'filesystem'

maint: prefer 'file system' over 'filesystem'

* doc/posix-functions/fstatat.texi (fstatat): Likewise.
* doc/posix-functions/lstat.texi (lstat): Likewise.
* lib/file-has-acl.c (file_has_acl): Likewise.
* lib/fwriteerror.c [TEST]: Likewise.
* tests/test-areadlink.h (test_areadlink): Likewise.
* tests/test-areadlinkat-with-size.c (main): Likewise.
* tests/test-areadlinkat.c (main): Likewise.
* tests/test-canonicalize-lgpl.c (main): Likewise.
* tests/test-canonicalize.c (main): Likewise.
* tests/test-fstatat.c (main): Likewise.
* tests/test-linkat.c (main): Likewise.
* tests/test-lstat.h (test_lstat_func): Likewise.
* tests/test-mkdir.h (test_mkdir): Likewise.
* tests/test-readlink.h (test_readlink): Likewise.
* tests/test-remove.c (main): Likewise.
* tests/test-rename.h (test_rename): Likewise.
* tests/test-renameat.c (main): Likewise.
* tests/test-rmdir.h (test_rmdir_func): Likewise.
* tests/test-symlink.h (test_symlink): Likewise.
* tests/test-symlinkat.c (main): Likewise.
* tests/test-unlink.h (test_unlink_func): Likewise.
* tests/test-unlinkat.c (main): Likewise.

Signed-off-by: Eric Blake <ebb9@byu.net>