Document building documentation
Move docstrings to their own files.

This way docstrings are much prettier to look at and easier to edit.
Python 2.4 compatibility
Move curl_*_new docstrings
Move pycurl module docstring to its own file, rename to pycurl_module_doc in the process
Document CurlShare in pycurl module
Extract curl object docstrings
Extract curl multi object docstrings
Extract curl share object docstrings