Issue #6236, #6348: Fix various failures in the io module under AIX

and other platforms, when using a non-gcc compiler. Patch by egreen.

In addition, I made explicit the signedness of all bitfields in the
IO library.

Misc/NEWS

@@ -379,6 +379,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #6236, #6348: Fix various failures in the `io` module under AIX
+  and other platforms, when using a non-gcc compiler. Patch by egreen.
+
 - Issue #6954: Fixed crash when using DISTUTILS_DEBUG flag in Distutils.
 
 - Issue #6851: Fix urllib.urlopen crash on secondairy threads on OSX 10.6

Modules/_io/fileio.c

@@ -45,10 +45,10 @@
 typedef struct {
 	PyObject_HEAD
 	int fd;
-	unsigned readable : 1;
-	unsigned writable : 1;
-	int seekable : 2; /* -1 means unknown */
-	int closefd : 1;
+	unsigned int readable : 1;
+	unsigned int writable : 1;
+	signed int seekable : 2; /* -1 means unknown */
+	unsigned int closefd : 1;
 	PyObject *weakreflist;
 	PyObject *dict;
 } fileio;

Modules/_io/textio.c

@@ -190,9 +190,9 @@ typedef struct {
     PyObject_HEAD
     PyObject *decoder;
     PyObject *errors;
-    int pendingcr:1;
-    int translate:1;
-    unsigned int seennl:3;
+    signed int pendingcr: 1;
+    signed int translate: 1;
+    unsigned int seennl: 3;
 } nldecoder_object;
 
 static int