libnl: depend on host-bison

libnl build breaks with bison <2.4 with:

bison -y -d  -o route/cls/ematch_syntax.c route/cls/ematch_syntax.y
route/cls/ematch_syntax.y:31.9-16: syntax error, unexpected
identifier, expecting string

So build our own known good version and use instead.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/libnl/libnl.mk

@@ -8,6 +8,7 @@ LIBNL_VERSION = 3.0
 LIBNL_SOURCE = libnl-$(LIBNL_VERSION).tar.gz
 LIBNL_SITE = http://www.infradead.org/~tgr/libnl/files/
 LIBNL_INSTALL_STAGING = YES
+LIBNL_DEPENDENCIES = host-bison
 
 define LIBNL_UNINSTALL_TARGET_CMDS
 	rm -f $(TARGET_DIR)/usr/lib/libnl.so*