[PATCH 2 of 2] Pure python base85 fallback

[Dennis Brakhane]

BTW, what is mercurial's policy regarding psyco? A
try:
    import psyco
    psyco.full() # or psyco.bind(...)
except ImportError: # or even Exception
    pass
should speed up this kind of code nicely (it sure did speed up my
Python Ascii85 implementation)