Remove unused <sys/acl.h> based code

Starting with commit v4.6-240-g5afdf12, nobody compiles this
non-Linux code.

* configure.ac (AC_CHECK_HEADERS): Remove sys/acl.h.
* file.c [HAVE_SYS_ACL_H]: Remove.
* xlat/aclcmds.in: Remove.
3 files changed