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/010-fallocate.patch

@@ -0,0 +1,14 @@
+--- tgt-1.0.42/usr/util.h.orig	2013-12-26 16:18:54.000000000 +0200
++++ tgt-1.0.42/usr/util.h	2013-12-26 16:19:10.000000000 +0200
+@@ -212,11 +212,6 @@
+  */
+ static inline int unmap_file_region(int fd, off_t offset, off_t length)
+ {
+-#ifdef FALLOC_FL_PUNCH_HOLE
+-	if (fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
+-			offset, length) == 0)
+-		return 0;
+-#endif
+ 	return -1;
+ }
+