set hg revision in Gajim version

autogen.sh

 #!/usr/bin/env bash
+  gajimversion="0.13.90"
+  if [ -d ".hg" ]; then
+    hgversion="-$(hexdump -n6 -e'6/1 "%02x"' .hg/dirstate)"
+  else
+    hgversion=""
+  fi
+  echo "define([AC_PACKAGE_VERSION], [${gajimversion}${hgversion}])" > m4/hgversion.m4
+
   AM_ARGS="--add-missing --gnu --copy"
   CONF_ARGS=""
   if test x`uname -s 2>/dev/null` = 'xDarwin' -a -f /Library/Frameworks/GTK+.framework/Versions/Current/env; then

configure.ac

 AC_INIT([Gajim - A Jabber Instant Messager],
-		[0.13.90],[http://trac.gajim.org/],[gajim])
+		["version-set-in-hgversion"],[http://trac.gajim.org/],[gajim])
 AC_PREREQ([2.59])
 
 AC_CONFIG_HEADER(config.h)

m4/acinclude.m4

@@ -47,3 +47,8 @@ AC_DEFUN([AS_AC_EXPAND],
   prefix=$prefix_save
   exec_prefix=$exec_prefix_save
 ])
+
+# Fix autoconf: They don't allow shell variables in AC_INIT
+# So we have to define them via m4 to be accepted....
+
+m4_include(m4/hgversion.m4)