add an import to work with newer cython, and other changes

Need to import malloc and free. (from libc.stdlib cimport malloc, free).
This also contains some other changes, mostly cython code to compute
character sums.
Adding conversion from sage characters.

This is ugly, and possibly prone to breaking. Maybe it is already
broken.
Fix conversion. Fix problems with 0.

The conversion was wrong. Now maybe it is right. I tested that
converting and then converting back gives the same thing for all
characters with modulus up to 1000.

Also, there was an infinite loop when trying to construct a Dirichlet
Group with modulus 0. Now we check that the modulus is positive.
export methods order(), invariants() and gens()

+ disable precomputations for large moduli
remove assert debug checks
add dummy logvalue computation for large moduli
Correct mathematical error on zeta_order
add simple tests
Merge branch 'master' into pascal

Conflicts:
	dirichlet_conrey.pyx
Change 3 to 5; change precomputation to always on

3 is now used instead of 5 for the generator for powers of 2. This is
the "correct" choice, since it makes certain things much easier.
(Basically, this is because 5 is 1 mod 4, so all powers of 5 are also 1
mod 4.)

This commit also sets precomputation to always happen again. Being able
to do things without precomputation is very important, and we want to
support it, but right now some important things are still broken if we
don't precompute, so it is always turned on.
Change author email.

I've changed the author email in the egg setup stuff that Fredrik wrote
to actually be by real email. (I don't know anything about this egg
stuff, though.)
added include dir '/src/sage/ext' which works for the new git version of sage