Disable unused stuff explicitely, cleanup package def, only install useful devel stuff

Signed-off-by: Nicolas Thill <nico@openwrt.org>

In order to reduce the dependencies, this patch disables following features:
 * Extended Attributes
 * ACL support
 * bzip2 through bz2lib
 * lzop through liblzo2
 * crypto support from Nettle
 * xar through libxml2

Signed-off-by: Johannes Morgenroth <morgenroth@ibr.cs.tu-bs.de>

Dependencies to libacl, libattr, libbz2, liblzo, and libnettle added.
PKG_BUILD_DEPENDS is removed since it is already defined by DEPENDS.

Signed-off-by: Johannes Morgenroth <morgenroth@ibr.cs.tu-bs.de>

This commit replaces the command with a more generic one.

Signed-off-by: Johannes Morgenroth <morgenroth@ibr.cs.tu-bs.de>

Multi-format archive and compression library

Signed-off-by: Johannes Morgenroth <morgenroth@ibr.cs.tu-bs.de>