replace thread state objects' ticker and checkinterval fields with two

globals, _Py_Ticker and _Py_CheckInterval.  This also implements Jeremy's
shortcut in Py_AddPendingCall that zeroes out _Py_Ticker.  This allows the
test in the main loop to only test a single value.

The gory details are at

    http://python.org/sf/602191

Include/ceval.h

@@ -48,6 +48,10 @@ PyAPI_FUNC(int) Py_GetRecursionLimit(void);
 PyAPI_FUNC(char *) PyEval_GetFuncName(PyObject *);
 PyAPI_FUNC(char *) PyEval_GetFuncDesc(PyObject *);
 
+/* this used to be handled on a per-thread basis - now just two globals */
+PyAPI_DATA(volatile int) _Py_Ticker;
+PyAPI_DATA(int) _Py_CheckInterval;
+
 /* Interface for threads.
 
    A module that plans to do a blocking system call (or something else

Include/pystate.h

@@ -22,7 +22,6 @@ typedef struct _is {
     PyObject *sysdict;
     PyObject *builtins;
 
-    int checkinterval;
 #ifdef HAVE_DLOPEN
     int dlopenflags;
 #endif
@@ -50,7 +49,6 @@ typedef struct _ts {
 
     struct _frame *frame;
     int recursion_depth;
-    int ticker;
     int tracing;
     int use_tracing;