tang: Add package into tree

Tang is lightweight server for binding data to network presence.
---
Tang's source: https://github.com/latchset/tang

Maintainer: @Tiboris

Compile tested: (mips, TL-WR842N, 17.01.4, r3560-79f57e422d)

**Tang requires a few other software libraries:**

1. libhttp-parser
2. xinetd's socket activation
3. jose >= 8

**Two new files compared to tang upstream:**
- tangdx : configuration file for xinetd
- tangdw : wrapper for tangd service
	- puts timestamp when service activated, and
	- redirects stderr to log file in /var/log/

**Removed systemd requirement**

Signed-off-by: Tibor Dudlák <tdudlak@redhat.com>

utils/tang/patches/Makefile_am.patch

@@ -0,0 +1,45 @@
+diff --git a/Makefile.am b/Makefile.am
+index 14bf91d..dfa6d07 100644
+--- a/Makefile.am
++++ b/Makefile.am
+@@ -1,5 +1,3 @@
+-DISTCHECK_CONFIGURE_FLAGS = --with-systemdsystemunitdir=$$dc_install_base/$(systemdsystemunitdir)
+-
+ AM_CFLAGS = @TANG_CFLAGS@ @jose_CFLAGS@
+ LDADD = @jose_LIBS@ @http_parser_LIBS@
+ 
+@@ -7,21 +5,11 @@ nagiosdir = $(libdir)/nagios/plugins
+ cachedir = $(localstatedir)/cache/$(PACKAGE_NAME)
+ jwkdir = $(localstatedir)/db/$(PACKAGE_NAME)
+ 
+-nodist_systemdsystemunit_DATA = \
+-    units/tangd@.service \
+-    units/tangd.socket \
+-    units/tangd-update.path \
+-    units/tangd-update.service \
+-    units/tangd-keygen.service
+-
+ dist_libexec_SCRIPTS = src/tangd-update src/tangd-keygen
+ libexec_PROGRAMS = src/tangd
+-nagios_PROGRAMS = src/tang
+-man1_MANS = doc/tang-nagios.1
+ man8_MANS = doc/tang.8
+ 
+ src_tangd_SOURCES = src/http.c src/http.h src/tangd.c
+-src_tang_SOURCES = src/nagios.c
+ 
+ %: %.in
+ 	$(AM_V_GEN)mkdir -p "`dirname "$@"`"
+@@ -32,11 +20,9 @@ src_tang_SOURCES = src/nagios.c
+ 		$(srcdir)/$@.in > $@
+ 
+ AM_TESTS_ENVIRONMENT = SD_ACTIVATE="@SD_ACTIVATE@" PATH=$(srcdir)/src:$(builddir)/src:$(PATH)
+-TESTS = tests/adv tests/rec tests/nagios
++TESTS = tests/adv tests/rec 
+ 
+-CLEANFILES = $(nodist_systemdsystemunit_DATA)
+ EXTRA_DIST = \
+-    $(foreach unit,$(nodist_systemdsystemunit_DATA),$(unit).in) \
+     COPYING \
+     $(TESTS) \
+     $(man1_MANS) \

utils/tang/patches/rm-systemd-from-configure.patch

@@ -0,0 +1,37 @@
+diff --git a/configure.ac b/configure.ac
+index b51bb31..4b37d30 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -27,32 +27,6 @@ AC_CHECK_LIB([http_parser], [http_parser_execute],
+              [AC_MSG_ERROR([http-parser required!])])
+ 
+ PKG_CHECK_MODULES([jose], [jose >= 8])
+-PKG_CHECK_MODULES([systemd], [systemd])
+-
+-AC_ARG_WITH([systemdsystemunitdir],
+-            [AS_HELP_STRING([--with-systemdsystemunitdir=DIR], [Directory for systemd service files])],
+-            [],
+-            [with_systemdsystemunitdir=$($PKG_CONFIG --variable=systemdsystemunitdir systemd)])
+-
+-AC_SUBST([systemdsystemunitdir], [$with_systemdsystemunitdir])
+-
+-for ac_prog in systemd-socket-activate systemd-activate; do
+-    AC_CHECK_PROG([SD_ACTIVATE], [$ac_prog], [$as_dir/$ac_prog], [],
+-		  [$PATH$PATH_SEPARATOR$($PKG_CONFIG --variable=systemdutildir systemd)])
+-    test -n "$SD_ACTIVATE" && break
+-done
+-
+-test -n "$SD_ACTIVATE" || AC_MSG_ERROR([systemd-socket-activate required!])
+-
+-AC_MSG_CHECKING([systemd-socket-activate inetd flag])
+-if $SD_ACTIVATE --help | grep -q inetd; then
+-    SD_ACTIVATE="$SD_ACTIVATE --inetd"
+-    AC_MSG_RESULT([--inetd])
+-else
+-    AC_MSG_RESULT([(default)])
+-fi
+-
+-AC_SUBST(SD_ACTIVATE)
+ 
+ TANG_CFLAGS="\
+ -Wall \

utils/tang/patches/use-readlink-in-tangd-update.patch

@@ -0,0 +1,15 @@
+diff --git a/src/tangd-update b/src/tangd-update
+index 652dbef..01aa842 100755
+--- a/src/tangd-update
++++ b/src/tangd-update
+@@ -33,8 +33,8 @@ fi
+ 
+ [ ! -d "$2" ] && mkdir -p -m 0700 "$2"
+ 
+-src=`realpath "$1"`
+-dst=`realpath "$2"`
++src=`readlink -f "$1"`
++dst=`readlink -f "$2"`
+ 
+ payl=()
+ sign=()