Fix for sympy 0.7.2

The git version of sympy allows to pass unicode for Symbols, but in order for
CSymPy to work also with 0.7.2, we simply convert unicode to str in Python 2.7.
Fix for Python lib called libpython3.2m.a

It seems we need to check for both libpython3.2.a and libpython3.2m.a.