PyThreadState_Swap(NULL) didn't do what I thought it did.  Fixes

[ 987287 ] Python 2.4a1, interpreter hanging on Keyboard Interrupt
diff --git a/Parser/myreadline.c b/Parser/myreadline.c
index 979e34f..7fc421e 100644
--- a/Parser/myreadline.c
+++ b/Parser/myreadline.c
@@ -84,7 +84,7 @@
 			int s;
 			PyEval_RestoreThread(_PyOS_ReadlineTState);
 			s = PyErr_CheckSignals();
-			PyThreadState_Swap(NULL);
+			PyEval_SaveThread();
 			if (s < 0) {
 				return 1;
 			}