Python 2 to 3 migration - m4 folder (#144)

Update cython.m4 and pythonhead.m4 files to be compatible with py2/3

pythonhead.m4 changes taken from:
  https://raw.githubusercontent.com/posborne/dbus-python/master/m4/am-check-python-headers.m4

cython.m4 changes taken from:
  https://raw.githubusercontent.com/alisw/rivet/master/m4/cython.m4

m4/cython.m4

@@ -1,23 +1,36 @@
-dnl a macro to check for the installed Cython version; note PYTHON needs to
-dnl be set before this function is called.
-dnl  CYTHON_CHECK_VERSION([MIN-VERSION], [ACTION-IF-TRUE], [ACTION-IF-FALSE])
+dnl a macro to check for the installed Cython version
+dnl  CYTHON_CHECK_VERSION([VERSION [,[ACTION-IF-TRUE [,ACTION-IF-FALSE]]])
+dnl Check if a Cython version is installed
+dnl Defines CYTHON_VERSION and CYTHON_FOUND
+dnl taken from Enligntenment Foundation Libraries(GPL).
 AC_DEFUN([CYTHON_CHECK_VERSION],
- [prog="import re, sys
-from Cython.Compiler.Version import version
-def get_int(arg):
-    matched = re.match(r'\d+', arg)
-    if matched is None:
-        return 0
-    else:
-        return int(matched.group(0))
-# split strings by '.' and convert to numeric.  Append some zeros
-# because we need at least 4 digits for the hex conversion.
-ver = map(get_int, version.rstrip('abcdefghijklmnopqrstuvwxyz').split('.')) + [[0, 0, 0]]
-verhex = 0
-for i in range(0, 4): verhex = (verhex << 8) + ver[[i]]
-minver = map(get_int, '$1'.split('.')) + [[0, 0, 0]]
-minverhex = 0
-for i in range(0, 4): minverhex = (minverhex << 8) + minver[[i]]
-sys.exit(verhex < minverhex)"
-  AS_IF([AM_RUN_LOG([$PYTHON -c "$prog"])], [$2], [$3])])
+[
+AC_REQUIRE([AM_PATH_PYTHON])
+ifelse([$1], [], [_msg=""], [_msg=" >= $1"])
+AC_MSG_CHECKING(for Cython$_msg)
+AC_CACHE_VAL(py_cv_cython, [
 
+prog="from __future__ import print_function; import Cython.Compiler.Version; print(Cython.Compiler.Version.version)"
+CYTHON_VERSION=`$PYTHON -c "$prog" 2>&AC_FD_CC`
+
+py_cv_cython=no
+if test "x$CYTHON_VERSION" != "x"; then
+   py_cv_cython=yes
+fi
+
+if test "x$py_cv_cython" = "xyes"; then
+   ifelse([$1], [], [:],
+      [AS_VERSION_COMPARE([$CYTHON_VERSION], [$1], [py_cv_cython=no])])
+fi
+])
+
+AC_MSG_RESULT([$py_cv_cython])
+
+if test "x$py_cv_cython" = "xyes"; then
+   CYTHON_FOUND=yes
+   ifelse([$2], [], [:], [$2])
+else
+   CYTHON_FOUND=no
+   ifelse([$3], [], [AC_MSG_ERROR([Could not find usable Cython$_msg])], [$3])
+fi
+])

m4/pythonhead.m4

@@ -1,16 +1,39 @@
 dnl a macro to check for ability to create python extensions
 dnl  AM_CHECK_PYTHON_HEADERS([ACTION-IF-POSSIBLE], [ACTION-IF-NOT-POSSIBLE])
 dnl function also defines PYTHON_INCLUDES
+dnl update taken from dbus-python(GPL).
 AC_DEFUN([AM_CHECK_PYTHON_HEADERS],
 [AC_REQUIRE([AM_PATH_PYTHON])
-AC_MSG_CHECKING(for headers required to compile python extensions)
+
+AC_PATH_PROGS([PYTHON_CONFIG], [python${PYTHON_VERSION}-config python-config], [no])
+if test "${PYTHON_CONFIG}" = "no"; then
+  AC_MSG_ERROR([cannot find python${PYTHON_VERSION}-config or python-config in PATH])
+fi
+
+AC_ARG_VAR([PYTHON_INCLUDES], [CPPFLAGS for Python, overriding output of python2.x-config --includes, e.g. "-I/opt/misc/include/python2.7"])
+
+if test "${PYTHON_INCLUDES+set}" = set; then
+  AC_MSG_NOTICE([PYTHON_INCLUDES overridden to: $PYTHON_INCLUDES])
+else
   dnl deduce PYTHON_INCLUDES
-py_prefix=`$PYTHON -c "import sys; print sys.prefix"`
-py_exec_prefix=`$PYTHON -c "import sys; print sys.exec_prefix"`
+  AC_MSG_CHECKING(for Python headers using $PYTHON_CONFIG --includes)
+  PYTHON_INCLUDES=`$PYTHON_CONFIG --includes`
+  if test $? = 0; then
+    AC_MSG_RESULT($PYTHON_INCLUDES)
+  else
+    AC_MSG_RESULT([failed, will try another way])
+    py_prefix=`$PYTHON -c "import sys; print(sys.prefix)"`
+    py_exec_prefix=`$PYTHON -c "import sys; print(sys.exec_prefix)"`
+    AC_MSG_CHECKING(for Python headers in $py_prefix and $py_exec_prefix)
     PYTHON_INCLUDES="-I${py_prefix}/include/python${PYTHON_VERSION}"
     if test "$py_prefix" != "$py_exec_prefix"; then
       PYTHON_INCLUDES="$PYTHON_INCLUDES -I${py_exec_prefix}/include/python${PYTHON_VERSION}"
     fi
+    AC_MSG_RESULT($PYTHON_INCLUDES)
+  fi
+fi
+
+AC_MSG_CHECKING(whether those headers are sufficient)
 AC_SUBST(PYTHON_INCLUDES)
 dnl check if the headers exist:
 save_CPPFLAGS="$CPPFLAGS"