pre C++11 fix for aabb.c and division by 0 fix

- Changed the aabb.c the fminf / fmaxf function (that is not supported in VS2010 as it is a C++11 addition) for a (a<b):?a:b; 
- Added some division by 0 checks to C++ classes 
- Fixed function constness for vec*::operator== 
- Added the vec*::operator!=