acl: add license information

Add missing license info and file for package 'acl'

[Peter: change to '+' version of licenses]
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/acl/acl.mk

@@ -10,6 +10,8 @@ ACL_SITE = http://download.savannah.gnu.org/releases/acl
 ACL_INSTALL_STAGING = YES
 ACL_DEPENDENCIES = attr
 ACL_CONF_OPT = --enable-gettext=no
+ACL_LICENSE = GPLv2+, LGPLv2.1+
+ACL_LICENSE_FILES = doc/COPYING doc/COPYING.LGPL
 
 # While the configuration system uses autoconf, the Makefiles are
 # hand-written and do not use automake. Therefore, we have to hack