Added and documented the capability for shlex to handle lexical-level
inclusion and a stack of input sources. Also, the input stream member
is now documented, and the constructor takes an optional source-filename.
The class provides facilities to generate error messages that track
file and line number.
[GvR: I changed the __main__ code so that it actually stops at EOF, as
Eric surely intended -- however it returned '' instead of the None he
was testing for.]
The attached patches update the standard library so that all modules
have docstrings beginning with one-line summaries.
A new docstring was added to formatter. The docstring for os.py
was updated to mention nt, os2, ce in addition to posix, dos, mac.
