Hyphenation

[Luís Marques]

"non-zero" seemed more natural to me than "nonzero", but after reading on the subject I've become convinced that nonzero is the way forward. (I've kept "non-zero" and added new instances of it on chapter 37, for consistency with the current choice).

• Alexandrescu uses nonzero on its D book

• http://english.stackexchange.com/questions/88085/hyphens-after-the-prefixes-non-and-anti-in-mathematics

• http://www-cs-faculty.stanford.edu/~uno/email.html

• http://gcc.gnu.org/ml/gcc/2001-10/msg00610.html

• etc (feel free to add)

[acehreli]

https://bitbucket.org/acehreli/ddili/commits/c2ec3c1ddc846646e7736d8a5eacf2fd444b952f