osutil: make statfiles check for interrupts periodically

This is a simpler and faster fix for issue4878 than the contortions
performed in 502b56a9e897.

mercurial/osutil.c

@@ -613,6 +613,11 static PyObject *statfiles(PyObject *sel
 		int ret, kind;
 		char *path;
 
+		/* With a large file count or on a slow filesystem,
+		   don't block signals for long (issue4878). */
+		if ((i % 1000) == 999 && PyErr_CheckSignals() == -1)
+			goto bail;
+
 		pypath = PySequence_GetItem(names, i);
 		if (!pypath)
 			goto bail;