Issue #4705: Fix the -u ("unbuffered binary stdout and stderr") command-line
flag to work properly. Furthermore, when specifying -u, the text stdout
and stderr streams have line-by-line buffering enabled (the default being
to buffer arbitrary chunks of data). Patch by Victor Stinner, test by me.
diff --git a/Include/pydebug.h b/Include/pydebug.h
index cd56196..0a31f5b 100644
--- a/Include/pydebug.h
+++ b/Include/pydebug.h
@@ -18,6 +18,7 @@
 PyAPI_DATA(int) Py_DivisionWarningFlag;
 PyAPI_DATA(int) Py_DontWriteBytecodeFlag;
 PyAPI_DATA(int) Py_NoUserSiteDirectory;
+PyAPI_DATA(int) Py_UnbufferedStdioFlag;
 
 /* this is a wrapper around getenv() that pays attention to
    Py_IgnoreEnvironmentFlag.  It should be used for getting variables like