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.

Python/errors.c

@@ -16,6 +16,11 @@ extern char *strerror(int);
 
 #include <ctype.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
 void
 PyErr_Restore(PyObject *type, PyObject *value, PyObject *traceback)
 {
@@ -786,3 +791,8 @@ PyErr_ProgramText(const char *filename, int lineno)
 	}
 	return NULL;
 }
+
+#ifdef __cplusplus
+}
+#endif
+