rsync: enable selecting bundled or system zlib

rsync, by default, includes a patched zlib within its source tarball. The patch
enables a better compression ratio for rsync streams. However, the client and
server need the same featureset in their zlib in order to understand the
compression stream, or the server will abort the transfer. Older versions have
no understanding of the new compression standard used.

This patch allows the builder to choose whether to use the bundled or system
zlib. It defautls to using the system zlib, as is the default before this
patch.

Signed-off-by: Ian Leonard <antonlacon@gmail.com>

net/rsync/Config.in

 		bool
 		prompt "Enable ACL support"
 		default n
+
+	config RSYNC_zlib
+		bool
+		prompt "Enable system zlib"
+		help 
+			Use the system's zlib library instead of rsync's internal copy. Enabling
+			this may create compatibility errors when using compression  with older
+			clients, or those using the current default of the bundled zlib.
+
+			rsync's upstream default is to use their bundled zlib. OpenWrt uses the
+			system zlib for space reasons. The system zlib will eventually become 
+			default for upstream as well.
+		default y
 endif

net/rsync/Makefile

   CATEGORY:=Network
   SUBMENU:=File Transfer
   TITLE:=Fast remote file copy program (like rcp)
-  DEPENDS:=+libpopt +zlib +RSYNC_xattr:libattr +RSYNC_acl:libacl
+  DEPENDS:=+libpopt +RSYNC_xattr:libattr +RSYNC_acl:libacl +RSYNC_zlib:zlib
   URL:=http://rsync.samba.org/
   MENU:=1
 endef
 	source "$(SOURCE)/Config.in"
 endef
 
+CONFIGURE_ARGS += \
+	--with-included-popt=no \
+	--disable-debug \
+	--disable-locale \
+
 ifeq ($(CONFIG_RSYNC_xattr),y)
 	CONFIGURE_ARGS+= --enable-xattr-support
 else
 	CONFIGURE_ARGS+= --disable-acl-support
 endif
 
+ifeq ($(CONFIG_RSYNC_zlib),y)
+	CONFIGURE_ARGS+= --with-included-zlib=no
+else
+	CONFIGURE_ARGS+= --with-included-zlib=yes
+endif
+
 define Package/rsyncd
   SECTION:=net
   CATEGORY:=Network
  between two sets of files across the network link.
 endef
 
-CONFIGURE_ARGS += \
-	--with-included-popt=no \
-	--with-included-zlib=no \
-	--disable-debug \
-	--disable-locale \
-
 define Package/rsync/install
 	$(INSTALL_DIR) $(1)/usr/bin
 	$(INSTALL_BIN) $(PKG_INSTALL_DIR)/usr/bin/$(PKG_NAME) $(1)/usr/bin/