bpo-38738: Fix formatting of True and False. (GH-17083)

* "Return true/false" is replaced with "Return ``True``/``False``"
  if the function actually returns a bool.
* Fixed formatting of some True and False literals (now in monospace).
* Replaced "True/False" with "true/false" if it can be not only bool.
* Replaced some 1/0 with True/False if it corresponds the code.
* "Returns <bool>" is replaced with "Return <bool>".
diff --git a/Doc/library/fileinput.rst b/Doc/library/fileinput.rst
index 8870c17..236f5d5 100644
--- a/Doc/library/fileinput.rst
+++ b/Doc/library/fileinput.rst
@@ -109,14 +109,14 @@
 
 .. function:: isfirstline()
 
-   Returns true if the line just read is the first line of its file, otherwise
-   returns false.
+   Return ``True`` if the line just read is the first line of its file, otherwise
+   return ``False``.
 
 
 .. function:: isstdin()
 
-   Returns true if the last line was read from ``sys.stdin``, otherwise returns
-   false.
+   Return ``True`` if the last line was read from ``sys.stdin``, otherwise return
+   ``False``.
 
 
 .. function:: nextfile()