In the old compiler, there was a optimization in
com_factor that folded a unary minus against a constant.

In the new AST, it looks like numbers are converted
from strings into PyObjects earlier in the pipeline. 
The compiler does fold a unary minus against a
constant, but since the PyObject has already been
created, it may return a PyLong when a PyInt is
sufficient.  This patch adds a check that will convert
a PyLong object back into a PyInt if possible.