Fix build on Python 3.x by using sys.maxsize. (#30424)

As outlined in https://docs.python.org/3.1/whatsnew/3.0.html#integers,
sys.maxint doesn't exist anymore in Python 3.x because there is no maximum
value for integers in Python 3.x.  sys.maxsize is present in all
versions of Python that are currently supported by Ansible, so use that
instead as an arbitrarily large index value.

Fixes the following build error when building with Python 3.x:
make -j1 docs
mkdir -p ./docs/man/man1/ ; \
PYTHONPATH=./lib docs/bin/generate_man.py --template-file=docs/templates/man.j2 --output-dir=docs/man/man1/ --output-format man lib/ansible/cli/*.py
Traceback (most recent call last):
  File "docs/bin/generate_man.py", line 253, in <module>
    allvars[cli_name] = opts_docs(cli_class_name, cli_name)
  File "docs/bin/generate_man.py", line 119, in opts_docs
    'long_desc': trim_docstring(cli.__doc__),
  File "docs/bin/generate_man.py", line 34, in trim_docstring
    indent = sys.maxint
AttributeError: module 'sys' has no attribute 'maxint'
make: *** [Makefile:347: generate_asciidoc] Error 1

docs/bin/generate_man.py

@@ -31,14 +31,14 @@ def trim_docstring(docstring):
     # and split into a list of lines:
     lines = docstring.expandtabs().splitlines()
     # Determine minimum indentation (first line doesn't count):
-    indent = sys.maxint
+    indent = sys.maxsize
     for line in lines[1:]:
         stripped = line.lstrip()
         if stripped:
             indent = min(indent, len(line) - len(stripped))
     # Remove indentation (first line is special):
     trimmed = [lines[0].strip()]
-    if indent < sys.maxint:
+    if indent < sys.maxsize:
         for line in lines[1:]:
             trimmed.append(line[indent:].rstrip())
     # Strip off trailing and leading blank lines: