Revert all usages of gcc's __extension__ keyword, and instead assert

that our headers are not built with __GNUC__ and __STRICT_ANSI__.

__extension__ had some weird (and buggy) behaviours when nested which
make it a risky proposition for general usage in our header
files. Better to disallow -ansi, -std=c99, and similar gcc options
when building against Xen headers.

Signed-off-by: Keir Fraser <keir.fraser@citrix.com>

tools/python/xen/xm/messages/xen-xm.pot

@@ -8,7 +8,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: PACKAGE VERSION\n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2007-04-05 14:17-0400\n"
+"POT-Creation-Date: 2008-03-31 17:40+0100\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
@@ -61,3 +61,8 @@ msgid ""
 "The network you specified already has a PIF attached to it, and so another "
 "one may not be attached."
 msgstr ""
+
+#: xen/xm/XenAPI.py:67
+#, python-format
+msgid "%(2)s"
+msgstr ""