Bump python to 3.5

3.5 release is needed for MSVC 14.0 (aka VS 2015) support. Python 3.5
removed build toolchain support for MSVC 2013. Because we still need
to support it, we duplicate the Python directory in externals and
copy old patches and dispatch to this directory for MSVC 2013. Once
the support for MSVC 2013 is dropped on master, this directory can be
removed again.

Change-Id: Idf7bc351239582f583ecbdb53c923cbdcf968089
Reviewed-on: https://gerrit.libreoffice.org/17352
Reviewed-by: Michael Stahl <mstahl@redhat.com>
Tested-by: Michael Stahl <mstahl@redhat.com>

external/python33/python-3.3.0-pythreadstate.patch.1

@@ -0,0 +1,15 @@
+disable a check in PyThreadState_Swap that is hopefully not a "real" problem
+
+--- python3/Python/pystate.c	2013-04-17 22:45:00.799800000 +0200
++++ python3/Python/pystate.c	2013-04-17 22:46:53.743800000 +0200
+@@ -437,7 +437,9 @@
+        to be used for a thread.  Check this the best we can in debug
+        builds.
+     */
+-#if defined(Py_DEBUG) && defined(WITH_THREAD)
++#if defined(Py_DEBUG) && defined(WITH_THREAD) && 0
++    /* disable this for LO - it is triggered by nested PyThreadAttach
++       which do not appear to be a real problem */
+     if (newts) {
+         /* This can be called from PyEval_RestoreThread(). Similar
+            to it, we need to ensure errno doesn't change.