Add a gitignore for some generated files.

The copy of Python we have checked out doesn't include a gitignore.

Change-Id: Ibd44be1051d3f4092f9f6aa97e05cbb51e83b8c8
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..e520a45
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+/Python-*/Lib/plat-win32/STDDEF.py
+/Python-*/Lib/plat-win32/regen
+/Python-*/Parser/pgen.stamp