configure: require python mako module

It is now a hard dependency because of the autogeneration of
format pack and unpack functions.

Update the documentation to reflect this change.

v2:
- Inline python script in m4 file and use PYTHON2

v3:

- Remove semicolons and quotes and change coding style
- Add Ilia Mirkin suggestion to use Python's split functionality.
- Use AX_CHECK_PYTHON_MAKO_MODULE name.
- Change to MIT license

Signed-off-by: Samuel Iglesias Gonsalvez <siglesias@igalia.com>
Reviewed-by: Jason Ekstrand <jason.ekstrand@intel.com>

m4/ax_check_python_mako_module.m4

@@ -0,0 +1,61 @@
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_CHECK_PYTHON_MAKO_MODULE(MIN_VERSION_NUMBER)
+#
+# DESCRIPTION
+#
+#   Check whether Python mako module is installed and its version higher than
+#   minimum requested.
+#
+#   Example of its use:
+#
+#   For example, the minimum mako version would be 0.7.3. Then configure.ac
+#   would contain:
+#
+#   AX_CHECK_PYTHON_MAKO_MODULE(0.7.3)
+#
+# LICENSE
+#
+#   Copyright (c) 2014 Intel Corporation.
+#
+#   Permission is hereby granted, free of charge, to any person obtaining a copy
+#   of this software and associated documentation files (the "Software"), to
+#   deal in the Software without restriction, including without limitation the
+#   rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+#   sell copies of the Software, and to permit persons to whom the Software is
+#   furnished to do so, subject to the following conditions:
+#
+#   The above copyright notice and this permission notice shall be included in
+#   all copies or substantial portions of the Software.
+#
+#   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+#   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+#   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+#   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+#   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+#   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+#   IN THE SOFTWARE.
+
+dnl macro that checks for mako module in python
+AC_DEFUN([AX_CHECK_PYTHON_MAKO_MODULE],
+[AC_MSG_CHECKING(if module mako in python is installed)
+    echo "
+try:
+    import sys
+    import mako
+except ImportError as err:
+    sys.exit(err)
+else:
+    ver_req = map(int, '$1'.split('.'))
+    ver_act = map(int, mako.__version__.split('.'))
+    sys.exit(int(ver_req > ver_act))
+    " | $PYTHON2 -
+
+    if test $? -ne 0 ; then
+       AC_MSG_ERROR(mako $1 or later is required.)
+    else
+        AC_MSG_RESULT(yes)
+    fi
+])