fix windows build using python 3.7

fixes NameError (missing "subprocess_main" and "basestring")

core/make_binders.py

@@ -1,6 +1,4 @@
 # -*- coding: ibm850 -*-
-from platform_methods import subprocess_main
-
 
 template_typed = """
 #ifdef TYPED_METHOD_BIND
@@ -274,4 +272,5 @@ def run(target, source, env):
 
 
 if __name__ == '__main__':
+    from platform_methods import subprocess_main
     subprocess_main(globals())

methods.py

@@ -6,12 +6,12 @@ import glob
 import string
 import datetime
 import subprocess
-from compat import iteritems
+from compat import iteritems, isbasestring
 
 
 def add_source_files(self, sources, filetype, lib_env=None, shared=False):
 
-    if isinstance(filetype, basestring):
+    if isbasestring(filetype):
         dir_path = self.Dir('.').abspath
         filetype = glob.glob(dir_path + "/" + filetype)