bpo-40204, doc: Fix syntax of C variables (GH-21846)

For example, fix the following Sphinx 3 errors:

Doc/c-api/buffer.rst:102: WARNING: Error in declarator or parameters
Invalid C declaration: Expected identifier in nested name. [error at 5]
  void \*obj
  -----^

Doc/c-api/arg.rst:130: WARNING: Unparseable C cross-reference: 'PyObject*'
Invalid C declaration: Expected end of definition. [error at 8]
  PyObject*
  --------^

The modified documentation is compatible with Sphinx 2 and Sphinx 3.

1 files changed, 3 insertions, 3 deletions

diff --git a/Doc/c-api/intro.rst b/Doc/c-api/intro.rst
index e89a788..7ca8693 100644
--- a/Doc/c-api/intro.rst
+++ b/Doc/c-api/intro.rst
@@ -229,13 +229,13 @@ Objects, Types and Reference Counts
 .. index:: object: type
 
 Most Python/C API functions have one or more arguments as well as a return value
-of type :c:type:`PyObject\*`.  This type is a pointer to an opaque data type
+of type :c:type:`PyObject*`.  This type is a pointer to an opaque data type
 representing an arbitrary Python object.  Since all Python object types are
 treated the same way by the Python language in most situations (e.g.,
 assignments, scope rules, and argument passing), it is only fitting that they
 should be represented by a single C type.  Almost all Python objects live on the
 heap: you never declare an automatic or static variable of type
-:c:type:`PyObject`, only pointer variables of type :c:type:`PyObject\*` can  be
+:c:type:`PyObject`, only pointer variables of type :c:type:`PyObject*` can  be
 declared.  The sole exception are the type objects; since these must never be
 deallocated, they are typically static :c:type:`PyTypeObject` objects.
 
@@ -496,7 +496,7 @@ Types
 
 There are few other data types that play a significant role in  the Python/C
 API; most are simple C types such as :c:type:`int`,  :c:type:`long`,
-:c:type:`double` and :c:type:`char\*`.  A few structure types  are used to
+:c:type:`double` and :c:type:`char*`.  A few structure types  are used to
 describe static tables used to list the functions exported  by a module or the
 data attributes of a new object type, and another is used to describe the value
 of a complex number.  These will  be discussed together with the functions that