Rewrite clean function since it was misbehaving and deleting files in an ignored directory.
build: update configure (unix) to accpept python 2.7 too

both python version 2.6, 2.7 are supported, there's little difference:
http://docs.python.org/dev/whatsnew/2.7.html#porting-to-python-2-7
enable python 2.6 / 2.7 in include header files

conditional include on _PY27 defined in configure if python is v2.7
make links for python2.7 -> python2.6 in external/ dir

this enables build with python2.7
not necessary after libs are modular
python 2.7: update readme for python 2.7 support
update boost to 1.52.0

need more recent version for compiler fixes/warnings, fixes, portability and other improvements
as of today, 1.53.0 is the latest version, but 1.52 is latest that builds without any modifications to the code.
Changelog can be found here: http://www.boost.org/users/history/
Merge branch 'master' into python27-support
Merge branch 'master' into python27-support
Merge pull request #85 from breznak/python27-support

Python27 support
Merge branch 'master' into recent-libs
Merge pull request #108 from breznak/recent-libs

Recent libs - boost 1.52
Merge branch 'master' into clean
Revert "Rewrite clean function since it was misbehaving and deleting files in an ignored directory."

This reverts commit c0d24ecc32c9f2a7ee852288454020ee3b88b037.
Create a copy of directory list for iteration.
Clean up the clean function (so meta).
Merge pull request #111 from scottpurdy/clean

Rewrite clean function since it was misbehaving and deleting files