Fix kmime build on OS X
Review Request #128285 - Created June 25, 2016 and discarded
Right now building kmime on OS X is failing because of ambiguity of type conversion from int to float, double or long double as there's no function 'abs' which takes 'int' as the parameter in <cmath>. Although in C++11, they had added overload for that but I don't know why it's not working on OS X. So, I have replaced <cmath> with <cstdlib> which does have 'abs' function which takes 'int' as the paramter.