[3.8] bpo-38738: Fix formatting of True and False. (GH-17083) (GH-17125)

* "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>".
(cherry picked from commit 138ccbb02216ca086047c3139857fb44f3dab1f9)
diff --git a/Doc/library/dataclasses.rst b/Doc/library/dataclasses.rst
index db5c3e0..9aa4a19 100644
--- a/Doc/library/dataclasses.rst
+++ b/Doc/library/dataclasses.rst
@@ -153,7 +153,7 @@
      method of the superclass will be used (if the superclass is
      :class:`object`, this means it will fall back to id-based hashing).
 
-   - ``frozen``: If true (the default is False), assigning to fields will
+   - ``frozen``: If true (the default is ``False``), assigning to fields will
      generate an exception.  This emulates read-only frozen instances.  If
      :meth:`__setattr__` or :meth:`__delattr__` is defined in the class, then
      :exc:`TypeError` is raised.  See the discussion below.
@@ -386,8 +386,8 @@
 
 .. function:: is_dataclass(class_or_instance)
 
-   Returns True if its parameter is a dataclass or an instance of one,
-   otherwise returns False.
+   Return ``True`` if its parameter is a dataclass or an instance of one,
+   otherwise return ``False``.
 
    If you need to know if a class is an instance of a dataclass (and
    not a dataclass itself), then add a further check for ``not