Increase version requirement for swig and add swig 3.0 detection

Change bindings test scripts to executable

configure.ac

@@ -616,7 +616,7 @@ AM_CONDITIONAL([ENABLE_LUA], [test x"${cf_with_lua_binding}" = "xyes"])
 dnl Only search for Swig if one or more bindings are enabled.
 AS_IF([test "x${BINDING_ALL}" != "x"],
     [# macros/ax_pkg_swig.m4
-    AX_PKG_SWIG([1.3.22],
+    AX_PKG_SWIG([3.0.12],
         [BINDINGS="${BINDINGS} bindings"
         cf_with_bindings="yes"],
         [AC_MSG_ERROR([SWIG is required to build bindings...])

macros/ax_pkg_swig.m4

@@ -66,8 +66,8 @@
 #serial 11
 
 AC_DEFUN([AX_PKG_SWIG],[
-        # Ubuntu has swig 2.0 as /usr/bin/swig2.0
-        AC_PATH_PROGS([SWIG],[swig swig2.0])
+        # Ubuntu has swig 3.0 as /usr/bin/swig3.0
+        AC_PATH_PROGS([SWIG],[swig swig3.0])
         if test -z "$SWIG" ; then
                 m4_ifval([$3],[$3],[:])
         elif test -n "$1" ; then