docs/library: Add CPython docs xref to each pertinent module.

Cross-reference text/link is implemented as RST substitution, so easy to consistently.

Author: pfalcon

docs/library/array.rst

@@ -4,8 +4,7 @@
 .. module:: array
  :synopsis: efficient arrays of numeric data
 
-See `Python array <https://docs.python.org/3/library/array.html>`_ for more
-information.
+|see_cpython_module| :mod:`python:array`.
 
 Supported format codes: ``b``, ``B``, ``h``, ``H``, ``i``, ``I``, ``l``,
 ``L``, ``q``, ``Q``, ``f``, ``d`` (the latter 2 depending on the

docs/library/builtins.rst

@@ -21,6 +21,8 @@ Functions and types
 
 .. class:: bytes()
 
+ |see_cpython| `python:bytes`.
+
 .. function:: callable()
 
 .. function:: chr()
@@ -174,6 +176,10 @@ Exceptions
 
 .. exception:: OSError
 
+ |see_cpython| `python:OSError`. MicroPython doesn't implement ``errno``
+ attribute, instead use the standard way to access exception arguments:
+ ``exc.args[0]``.
+
 .. exception:: RuntimeError
 
 .. exception:: StopIteration
@@ -182,8 +188,12 @@ Exceptions
 
 .. exception:: SystemExit
 
+ |see_cpython| `python:SystemExit`.
+
 .. exception:: TypeError
 
+ |see_cpython| `python:TypeError`.
+
 .. exception:: ValueError
 
 .. exception:: ZeroDivisionError

docs/library/cmath.rst

@@ -4,6 +4,8 @@
 .. module:: cmath
  :synopsis: mathematical functions for complex numbers
 
+|see_cpython_module| :mod:`python:cmath`.
+
 The ``cmath`` module provides some basic mathematical functions for
 working with complex numbers.
 

docs/library/gc.rst

@@ -4,6 +4,8 @@
 .. module:: gc
  :synopsis: control the garbage collector
 
+|see_cpython_module| :mod:`python:gc`.
+
 Functions
 ---------
 

docs/library/math.rst

@@ -4,6 +4,8 @@
 .. module:: math
  :synopsis: mathematical functions
 
+|see_cpython_module| :mod:`python:math`.
+
 The ``math`` module provides some basic mathematical functions for
 working with floating-point numbers.
 

docs/library/sys.rst

@@ -4,6 +4,8 @@
 .. module:: sys
  :synopsis: system specific functions
 
+|see_cpython_module| :mod:`python:sys`.
+
 Functions
 ---------
 

docs/library/ubinascii.rst

@@ -4,6 +4,8 @@
 .. module:: ubinascii
  :synopsis: binary/ASCII conversions
 
+|see_cpython_module| :mod:`python:binascii`.
+
 This module implements conversions between binary data and various
 encodings of it in ASCII form (in both directions).
 

docs/library/ucollections.rst

@@ -4,6 +4,8 @@
 .. module:: ucollections
  :synopsis: collection and container types
 
+|see_cpython_module| :mod:`python:collections`.
+
 This module implements advanced collection and container types to
 hold/accumulate various objects.
 

docs/library/uhashlib.rst

@@ -4,6 +4,8 @@
 .. module:: uhashlib
  :synopsis: hashing algorithms
 
+|see_cpython_module| :mod:`python:hashlib`.
+
 This module implements binary data hashing algorithms. The exact inventory
 of available algorithms depends on a board. Among the algorithms which may
 be implemented:

docs/library/uheapq.rst

@@ -4,6 +4,8 @@
 .. module:: uheapq
  :synopsis: heap queue algorithm
 
+|see_cpython_module| :mod:`python:heapq`.
+
 This module implements the heap queue algorithm.
 
 A heap queue is simply a list that has its elements stored in a certain way.