On Linux, use the getxattr syscall instead of the acl_extended_file libacl
library function to check for the presence of acls, avoiding a library
dependency.
* lib/file-has-acl.c: Include xattr headers if we have them.
(file_has_acl): On Linux, use getxattr().
* m4/acl.m4 (gl_FUNC_ACL): Define LIB_HAS_ACL as the libraries to link with for
file_has_acl(). Check for xattr headers and getxattr().
* modules/acl: Add a dep on the stdbool module which was already needed.
Add the new reduced dependency LIB_HAS_ACL reference.