Redo py3k branching from trunk again

[SVN r52115]
add brace around a Python print called in jam script since print become a function in py3k

[SVN r53276]
add 2to3 support for bpl-test

[SVN r55359]
some debugging code for python.jam and add a dummy enum.py as dependent of polymorphism2_auto_ptr for testing

[SVN r55360]
corrected python version checking for 2to3

[SVN r55441]