Bump lighttpd to 1.4.20.

Initial patch provided by Gustavo Zacarias <gustavo@zacarias.com.ar>.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/lighttpd/lighttpd.mk

@@ -3,7 +3,7 @@
 # lighttpd
 #
 #############################################################
-LIGHTTPD_VERSION:=1.4.19
+LIGHTTPD_VERSION:=1.4.20
 LIGHTTPD_SOURCE:=lighttpd-$(LIGHTTPD_VERSION).tar.bz2
 LIGHTTPD_SITE:=http://www.lighttpd.net/download
 LIGHTTPD_INSTALL_STAGING = NO