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/sys.rst b/Doc/library/sys.rst
index a2e930b..4b0bcde 100644
--- a/Doc/library/sys.rst
+++ b/Doc/library/sys.rst
@@ -1414,7 +1414,7 @@
      On Windows, UTF-8 is used for the console device.  Non-character
      devices such as disk files and pipes use the system locale
      encoding (i.e. the ANSI codepage).  Non-console character
-     devices such as NUL (i.e. where isatty() returns True) use the
+     devices such as NUL (i.e. where ``isatty()`` returns ``True``) use the
      value of the console input and output codepages at startup,
      respectively for stdin and stdout/stderr. This defaults to the
      system locale encoding if the process is not initially attached