adblock: reduce memory consumption

* rework shallalist processing: significantly reduce memory consumption
during archive extraction and merging.
* considerable reduce memory consumption during adblock source
processing.
* considerable reduce memory consumption of sort (sorts only the domain
list and not the bigger dnsmasq file)

other changes:
* auto detection/defaults for adb_if, adb_dev, adb_ntpsrv, adb_maxloop,
adb_maxtime and adb_minspace - these options can be safely removed from
previous adblock configuration file
* check total memory and main uhttpd configuration on startup
* documentation update

Signed-off-by: Dirk Brenken <dirk@brenken.org>

net/adblock/Makefile

@@ -7,7 +7,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=adblock
-PKG_VERSION:=0.21.0
+PKG_VERSION:=0.22.0
 PKG_RELEASE:=1
 PKG_LICENSE:=GPL-3.0+
 PKG_MAINTAINER:=Dirk Brenken <dirk@brenken.org>
@@ -23,7 +23,7 @@ define Package/$(PKG_NAME)
 endef
 
 define Package/$(PKG_NAME)/description
-powerful adblock script to block ad/abuse domains
+Powerful adblock script to block ad/abuse domains
 When the dns server on your router receives dns requests, we will sort out queries that ask for the [A]
 resource records of ad servers and return the local ip address of your router and the internal web server
 delivers a transparent pixel instead.
@@ -38,6 +38,8 @@ The script supports the following domain blacklist sites:
   http://www.spam404.com
   http://winhelp2002.mvps.org
 
+Please read README.md in /etc/adblock for further information.
+
 endef
 
 define Package/$(PKG_NAME)/conffiles