Fix AM_PATH_LIBGCRYPT not found

This patch installs a copy of libgcrypt.m4 from the libgcrypt source tarball
to systemd m4 directory.

Libgcrypt uses a custom m4 macro and not pkg-config to check if the
development files are available. Though libgcrypt support is optional in
systemd, this macro should be available whenever autoreconf is used, otherwise
the re-configuration will fail with:

  configure.ac:616: warning: macro 'AM_PATH_LIBGCRYPT' not found in library

As asking the user to install the development package of libgcrypt on the host
machine or adding libgcrypt as a build dependency to systemd is not
acceptable, the required file is added to the m4 directory.

Signed-off-by: Eric Le Bihan <eric.le.bihan.dev@free.fr>
Index: systemd-213/m4/libgcrypt.m4
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ systemd-213/m4/libgcrypt.m4	2014-06-11 10:41:11.749305509 +0200
@@ -0,0 +1,123 @@
+dnl Autoconf macros for libgcrypt
+dnl       Copyright (C) 2002, 2004 Free Software Foundation, Inc.
+dnl
+dnl This file is free software; as a special exception the author gives
+dnl unlimited permission to copy and/or distribute it, with or without
+dnl modifications, as long as this notice is preserved.
+dnl
+dnl This file is distributed in the hope that it will be useful, but
+dnl WITHOUT ANY WARRANTY, to the extent permitted by law; without even the
+dnl implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+
+
+dnl AM_PATH_LIBGCRYPT([MINIMUM-VERSION,
+dnl                   [ACTION-IF-FOUND [, ACTION-IF-NOT-FOUND ]]])
+dnl Test for libgcrypt and define LIBGCRYPT_CFLAGS and LIBGCRYPT_LIBS.
+dnl MINIMUN-VERSION is a string with the version number optionalliy prefixed
+dnl with the API version to also check the API compatibility. Example:
+dnl a MINIMUN-VERSION of 1:1.2.5 won't pass the test unless the installed
+dnl version of libgcrypt is at least 1.2.5 *and* the API number is 1.  Using
+dnl this features allows to prevent build against newer versions of libgcrypt
+dnl with a changed API.
+dnl
+AC_DEFUN([AM_PATH_LIBGCRYPT],
+[ AC_ARG_WITH(libgcrypt-prefix,
+            AC_HELP_STRING([--with-libgcrypt-prefix=PFX],
+                           [prefix where LIBGCRYPT is installed (optional)]),
+     libgcrypt_config_prefix="$withval", libgcrypt_config_prefix="")
+  if test x$libgcrypt_config_prefix != x ; then
+     if test x${LIBGCRYPT_CONFIG+set} != xset ; then
+        LIBGCRYPT_CONFIG=$libgcrypt_config_prefix/bin/libgcrypt-config
+     fi
+  fi
+
+  AC_PATH_TOOL(LIBGCRYPT_CONFIG, libgcrypt-config, no)
+  tmp=ifelse([$1], ,1:1.2.0,$1)
+  if echo "$tmp" | grep ':' >/dev/null 2>/dev/null ; then
+     req_libgcrypt_api=`echo "$tmp"     | sed 's/\(.*\):\(.*\)/\1/'`
+     min_libgcrypt_version=`echo "$tmp" | sed 's/\(.*\):\(.*\)/\2/'`
+  else
+     req_libgcrypt_api=0
+     min_libgcrypt_version="$tmp"
+  fi
+
+  AC_MSG_CHECKING(for LIBGCRYPT - version >= $min_libgcrypt_version)
+  ok=no
+  if test "$LIBGCRYPT_CONFIG" != "no" ; then
+    req_major=`echo $min_libgcrypt_version | \
+               sed 's/\([[0-9]]*\)\.\([[0-9]]*\)\.\([[0-9]]*\)/\1/'`
+    req_minor=`echo $min_libgcrypt_version | \
+               sed 's/\([[0-9]]*\)\.\([[0-9]]*\)\.\([[0-9]]*\)/\2/'`
+    req_micro=`echo $min_libgcrypt_version | \
+               sed 's/\([[0-9]]*\)\.\([[0-9]]*\)\.\([[0-9]]*\)/\3/'`
+    libgcrypt_config_version=`$LIBGCRYPT_CONFIG --version`
+    major=`echo $libgcrypt_config_version | \
+               sed 's/\([[0-9]]*\)\.\([[0-9]]*\)\.\([[0-9]]*\).*/\1/'`
+    minor=`echo $libgcrypt_config_version | \
+               sed 's/\([[0-9]]*\)\.\([[0-9]]*\)\.\([[0-9]]*\).*/\2/'`
+    micro=`echo $libgcrypt_config_version | \
+               sed 's/\([[0-9]]*\)\.\([[0-9]]*\)\.\([[0-9]]*\).*/\3/'`
+    if test "$major" -gt "$req_major"; then
+        ok=yes
+    else
+        if test "$major" -eq "$req_major"; then
+            if test "$minor" -gt "$req_minor"; then
+               ok=yes
+            else
+               if test "$minor" -eq "$req_minor"; then
+                   if test "$micro" -ge "$req_micro"; then
+                     ok=yes
+                   fi
+               fi
+            fi
+        fi
+    fi
+  fi
+  if test $ok = yes; then
+    AC_MSG_RESULT([yes ($libgcrypt_config_version)])
+  else
+    AC_MSG_RESULT(no)
+  fi
+  if test $ok = yes; then
+     # If we have a recent libgcrypt, we should also check that the
+     # API is compatible
+     if test "$req_libgcrypt_api" -gt 0 ; then
+        tmp=`$LIBGCRYPT_CONFIG --api-version 2>/dev/null || echo 0`
+        if test "$tmp" -gt 0 ; then
+           AC_MSG_CHECKING([LIBGCRYPT API version])
+           if test "$req_libgcrypt_api" -eq "$tmp" ; then
+             AC_MSG_RESULT([okay])
+           else
+             ok=no
+             AC_MSG_RESULT([does not match. want=$req_libgcrypt_api got=$tmp])
+           fi
+        fi
+     fi
+  fi
+  if test $ok = yes; then
+    LIBGCRYPT_CFLAGS=`$LIBGCRYPT_CONFIG --cflags`
+    LIBGCRYPT_LIBS=`$LIBGCRYPT_CONFIG --libs`
+    ifelse([$2], , :, [$2])
+    if test x"$host" != x ; then
+      libgcrypt_config_host=`$LIBGCRYPT_CONFIG --host 2>/dev/null || echo none`
+      if test x"$libgcrypt_config_host" != xnone ; then
+        if test x"$libgcrypt_config_host" != x"$host" ; then
+  AC_MSG_WARN([[
+***
+*** The config script $LIBGCRYPT_CONFIG was
+*** built for $libgcrypt_config_host and thus may not match the
+*** used host $host.
+*** You may want to use the configure option --with-libgcrypt-prefix
+*** to specify a matching config script.
+***]])
+        fi
+      fi
+    fi
+  else
+    LIBGCRYPT_CFLAGS=""
+    LIBGCRYPT_LIBS=""
+    ifelse([$3], , :, [$3])
+  fi
+  AC_SUBST(LIBGCRYPT_CFLAGS)
+  AC_SUBST(LIBGCRYPT_LIBS)
+])