Inspired by FreeBSD "ports".
Fix the PLISTs accordingly.
Also, while at it, remove now obsolete compileall.py calls in post-install
targets and insure that extension.mk is in included before builinlinks of
other Python modules.
Discussed with/ok'ed by drochner@.
Changes :
* Factored the help-formatting code out of OptionParser into
some new classes (HelpFormatter and subclasses) in help.py. This
should make it a lot easier to customize how help is formatted.
* Added the notion of "option groups": an OptionParser can now
contain several option groups, each which contains several options.
The main purpose of this is to enable sensibly-grouped help output,
but it opens up all sorts of interesting (and largely untested)
possibilities for code to throw whole option groups around instead
of individual options. Added two new classes: OptionGroup, and
OptionContainer for code common to OptionParser and OptionGroup.
(OptionContainer should be invisible to programmers using Optik).
* Added the 'description' attribute and set_description() method to
both OptionParser and OptionGroup (actually OptionContainer).
Again, this is to make help output more useful.
* Made it easier for OptionParser subclasses to decide whether
they should have the standard "help" option, by moving the logic
from class level to the _populate_option_list() method.
* Added the "choice" option type, which is just a string type
constrained to a fixed set of values.
* Added method get_default_values() to OptionParser.
* Rewrote how OptionParser recognizes abbreviated long
options; removed a redundant internal instance attribute.
* Simplify parsing logic in OptionParser a tad by relocating a loop
and renaming _process_arg() to _process_args().
