Support for installable libraries in numpy.distutils

This adds a new command install_clib
    - The library is built as a conventional C library (by the build_clib command)
    - It does respect the --record and works to build egg (at least on my configuration).
    - info necessary to build/link against those installed C libraries are handled through simple .ini files, and are retrieved through a simple function call.
    - both numpy.distutils and numscons builds are supported

Example of usage: see add_installed_library in numpy/core/setup.py. 

The npymath library can be reused as follows:

from numpy.distutils.misc_util import get_info

config.add_library('foo',
sources=['foo.c'],
extra_info=get_info('npymath'))

[cournape, 2009-07-08 11:27:33]

Updated patch

[cournape, 2009-07-09 07:11:07]

V3 of the patch: more docs + fixes for relative install directories

[charlesr.harris, 2009-07-13 05:33:41]

On 2009/07/09 07:11:07, cournape wrote:
> V3 of the patch: more docs + fixes for relative install directories

Hi David,

I just wrote a fairly long piece and then it disappeared. Argghhh. Anyway, the
upshot was that it might be useful for someone more familiar with distutils to
review the overall design, but that the patch was small enough that I don't
think you need to worry about merging it. If you are concerned about others
using it before the wrinkles are ironed out you could mark it experimental. No
doubt the next release of Scipy will be a good workout for the code.

Other than that, some meta-documentation would help build newbies like myself
get started, i.e., if I want to add a library and use it in another package,
what steps do I need to go through. Also, why did you do things the way you did,
what were the deficiencies of distutils that you needed to work around, and so
on. That information is sort of buried in comments along the way but it would be
helpful to bring it together in one place. As to the documentation of the
classes and functions, it looks a bit uneven. Some of it is complete but some of
it is also a bit on the terse side. Not that the current code is wonderfully
documented but we have to start somewhere ;)