tgt: iSCSI target support

This is a port from old packages repo with the following improvements:
- allow to select multiple addresses and ports to listent to
- support both address- and name-based ACLs
  (note: config option has been changed from "allow" to "allow_address", "allow_name")
- support more optionf for LUNs
- support various device types (disk, cd, sg passthrough)
- bind accounts to multiple targets
- use uci_validate_section in the init script
- improve error reporting, use logger instead of echo
- set number of IO threads to 2 by default (affects memory footprint)
- configure keepalive
- update to 1.0.48

Signed-off-by: Maxim Storchak <m.storchak@gmail.com>

net/tgt/patches/030-Makefile.patch

@@ -0,0 +1,11 @@
+--- tgt-1.0.46.orig/Makefile	2014-04-06 09:55:49.000000000 +0300
++++ tgt-1.0.46/Makefile	2014-04-06 09:57:04.000000000 +0300
+@@ -63,7 +63,7 @@
+ 	$(MAKE) -C conf clean
+ 
+ .PHONY: install
+-install: install-programs install-doc install-conf install-scripts
++install: install-programs
+ 
+ .PHONY: rpm
+ rpm: