misc: copy extended attributes in populate_fs

When creating a file system using a source directory, also copy any extended
attributes that have been set.

[ Add configure tests for Linux-specific xattr syscalls and add fallback
  when compiling on non-Linux systems. --tytso ]

Signed-off-by: Ross Burton <ross.burton@intel.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
4 files changed