spread the extern "C" { } magic pixie dust around. Python itself builds now

using a C++ compiler. Still lots and lots of errors in the modules built by
setup.py, and a bunch of warnings from g++ in the core.

Modules/posixmodule.c

@@ -22,6 +22,10 @@
 #    include <unixio.h>
 #endif /* defined(__VMS) */
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 PyDoc_STRVAR(posix__doc__,
 "This module provides access to operating system functionality that is\n\
 standardized by the C Standard and the POSIX standard (a thinly\n\
@@ -8253,3 +8257,8 @@ INITFUNC(void)
 	PyModule_AddObject(m, "statvfs_result",
 			   (PyObject*) &StatVFSResultType);
 }
+
+#ifdef __cplusplus
+}
+#endif
+