eliminate trailing spaces and normalize initial spacing of examples (some had five spaces, and the usual is four).

normalize text indentation, favoring not indenting expository text.  fix a few typos and spacing problems.

remove some superfluous whitespace, capitalize a comment, and normalize option error message to look like the ones in zc.buildout.

make a branch for the minor cleanup in gary-support-system-python branches.  this will be the base branch for my effort to break up the gary-support-system-python branch into five.

Revert to old style path.

- Incrementing didn't work properly when extending multiple files.
  https://bugs.launchpad.net/zc.buildout/+bug/421022

windows, urllib raises an invalid ioerror.

windows, urllib raises an invalid ioerror.

  The standard Python -m option didn't work for custom interpreters.

  Scripts run using generated interpreters didn't have __file__ set correctly.

  Scripts generated with relative-paths eanbled couldn't be
  symbolocally linked to other locations and still work.

  Option incrementing and decrementing didn't work for options
  specified on the command line.

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(Also stop writing doc.txt. --long-description is better. And
rearranged setup.py a little.)

- When doing variable substitutions, you can omit the section name to
  refer to a variable in the same section (e.g. ${:foo}).

- When doing variable substitution, you can use the special option,
  ``_buildout_section_name_`` to get the section name.  This is most handy
  for getting the current section name (e.g. ${:_buildout_section_name_}).

- A new special option, ``<`` allows sections to be used as macros.