Added support for two new standard errors: EnvironmentError and

OSError.  The EnvironmentError serves primarily as the (common
implementation) base class for IOError and OSError.  OSError is used
by posixmodule.c

Also added tuple definition of EnvironmentError when using string
based exceptions.

Python/bltinmodule.c

@@ -1935,7 +1935,9 @@ PyObject *PyExc_AssertionError;
 PyObject *PyExc_AttributeError;
 PyObject *PyExc_EOFError;
 PyObject *PyExc_FloatingPointError;
+PyObject *PyExc_EnvironmentError;
 PyObject *PyExc_IOError;
+PyObject *PyExc_OSError;
 PyObject *PyExc_ImportError;
 PyObject *PyExc_IndexError;
 PyObject *PyExc_KeyError;
@@ -1968,7 +1970,9 @@ bltin_exc[] = {
 	{"AttributeError",     &PyExc_AttributeError,     1},
 	{"EOFError",           &PyExc_EOFError,           1},
 	{"FloatingPointError", &PyExc_FloatingPointError, 1},
+	{"EnvironmentError",   &PyExc_EnvironmentError,   1},
 	{"IOError",            &PyExc_IOError,            1},
+	{"OSError",            &PyExc_OSError,            1},
 	{"ImportError",        &PyExc_ImportError,        1},
 	{"IndexError",         &PyExc_IndexError,         1},
 	{"KeyError",           &PyExc_KeyError,           1},
@@ -2078,11 +2082,11 @@ initerrors(dict)
 				newstdexception(dict, bltin_exc[i].name);
 	}
 
-	/* This is kind of bogus because we special case the three new
-	   exceptions to be nearly forward compatible.  But this means we
-	   hard code knowledge about exceptions.py into C here.  I don't
-	   have a better solution, though
-	*/
+	/* This is kind of bogus because we special case the some of the
+	 * new exceptions to be nearly forward compatible.  But this means
+	 * we hard code knowledge about exceptions.py into C here.  I don't
+	 * have a better solution, though.
+	 */
 	PyExc_LookupError = PyTuple_New(2);
 	Py_INCREF(PyExc_IndexError);
 	PyTuple_SET_ITEM(PyExc_LookupError, 0, PyExc_IndexError);
@@ -2099,6 +2103,13 @@ initerrors(dict)
 	PyTuple_SET_ITEM(PyExc_ArithmeticError, 2, PyExc_FloatingPointError);
 	PyDict_SetItemString(dict, "ArithmeticError", PyExc_ArithmeticError);
 
+	PyExc_EnvironmentError = PyTuple_New(2);
+	Py_INCREF(PyExc_IOError);
+	PyTuple_SET_ITEM(PyExc_EnvironmentError, 0, PyExc_IOError);
+	Py_INCREF(PyExc_OSError);
+	PyTuple_SET_ITEM(PyExc_EnvironmentError, 1, PyExc_OSError);
+	PyDict_SetItemString(dict, "EnvironmentError", PyExc_EnvironmentError);
+
 	PyExc_StandardError = PyTuple_New(exccnt-2);
 	for (i = 2; bltin_exc[i].name; i++) {
 		PyObject *exc = *bltin_exc[i].exc;