fix prototypes due to Windows support in fmpz_mod_poly.h, fmpz_mod_poly_factor.h, nmod_poly.h
cut off for using multithreaded distinct degree factorization
Merge branch 'cutoff' of https://github.com/mmklee/flint2 into trunk

Conflicts:
	fmpz_mod_poly.h
	nmod_poly.h