Correct a flaw in the Python 3 version checking

It turns out the ax_python_devel.m4 version check assumes that
("3.X+1.0" >= "3.X.0") is True in Python, which is not when X+1
is 10 or above and X is not. (Also presumably X+1=100 and ...)

So let's refactor the check to succeed then.

Signed-off-by: Rich Ercolani <rincebrain@gmail.com>

config/ax_python_devel.m4

@@ -127,8 +127,10 @@ to something else than an empty string.
 	if test -n "$1"; then
 		AC_MSG_CHECKING([for a version of Python $1])
 		ac_supports_python_ver=`$PYTHON -c "import sys; \
+			from packaging import version; \
 			ver = sys.version.split ()[[0]]; \
-			print (ver $1)"`
+			(tst_cmp,tst_ver) = \"$1\".split (); \
+			eval (\"print (version.parse (ver) \"+ tst_cmp +\" version.parse (tst_ver))\")"`
 		if test "$ac_supports_python_ver" = "True"; then
 		   AC_MSG_RESULT([yes])
 		else