git-p4: import the ctypes module

The ctypes module is used on windows to calculate free disk space,
so it must be imported.  We won't need it on other platforms, but
the module is available in Python 2.5 and newer, so importing it
unconditionally is harmless.

Signed-off-by: Dennis Kaarsemaker <dennis@kaarsemaker.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-p4.py

@@ -22,6 +22,7 @@
 import re
 import shutil
 import stat
+import ctypes
 
 try:
     from subprocess import CalledProcessError