Add const to several API functions that take char *.

In C++, it's an error to pass a string literal to a char* function
without a const_cast().  Rather than require every C++ extension
module to put a cast around string literals, fix the API to state the
const-ness.

I focused on parts of the API where people usually pass literals:
PyArg_ParseTuple() and friends, Py_BuildValue(), PyMethodDef, the type
slots, etc.  Predictably, there were a large set of functions that
needed to be fixed as a result of these changes.  The most pervasive
change was to make the keyword args list passed to
PyArg_ParseTupleAndKewords() to be a const char *kwlist[].

One cast was required as a result of the changes:  A type object
mallocs the memory for its tp_doc slot and later frees it.
PyTypeObject says that tp_doc is const char *; but if the type was
created by type_new(), we know it is safe to cast to char *.

1 files changed, 4 insertions, 3 deletions

diff --git a/Objects/fileobject.c b/Objects/fileobject.c
index 7e40547..259a423 100644
--- a/Objects/fileobject.c
+++ b/Objects/fileobject.c
@@ -1884,7 +1884,7 @@ file_init(PyObject *self, PyObject *args, PyObject *kwds)
 {
 	PyFileObject *foself = (PyFileObject *)self;
 	int ret = 0;
-	static char *kwlist[] = {"name", "mode", "buffering", 0};
+	static const char *kwlist[] = {"name", "mode", "buffering", 0};
 	char *name = NULL;
 	char *mode = "r";
 	int bufsize = -1;
@@ -1926,8 +1926,9 @@ file_init(PyObject *self, PyObject *args, PyObject *kwds)
 			return -1;
 
                 /* We parse again to get the name as a PyObject */
-                if (!PyArg_ParseTupleAndKeywords(args, kwds, "O|si:file", kwlist,
-                    &o_name, &mode, &bufsize))
+                if (!PyArg_ParseTupleAndKeywords(args, kwds, "O|si:file", 
+                                                 kwlist, &o_name, &mode, 
+                                                 &bufsize))
                         return -1;
 
 		if (fill_file_fields(foself, NULL, o_name, mode,