[Pyrex] More on enums in 0.9.5.1a

[Eric Huss]

Enum strictness seems to be a little too extreme in 0.9.5.1a.  Arithmetic
operations should be allowed on enums.  As far as my reading of the C++
standard, and reading from Stroustrup (The C++ Programming Language),
enums are implicitly converted to integers for arithmetic operations.
Also, implicit casts from enum->int are ok, such as in assignment (but the
inverse is not).  I believe the following errors in Pyrex should be
allowed:

cdef enum Color:
    red
    white
    blue

cdef Color e
cdef int i

i = red			# Fails.
i = red + 1		# Fails.
i = red | 1		# Fails.
e = white
i = e			# Fails.
i = e + 1		# Fails.

-Eric