1) fix all warnings in g++ -Wall -Wextra (#17)
1) fix all warnings in g++ -Wall -Wextra (#17)

2) fix in "inline double rho_pX" function
3) replaced pow(somethig, 0,5) with sqrt
4) replaced pow(somethig, 2) with something*something
5) std::vector::push_back replaced with reserve + emplace_back
6) some approaches to vectorize calculations in Region5::T_p(double p)
7) added const modifier in constant methods
8) some little optimizations
CoolProp/IF97,CoolProp/IF97,henningjp/IF97,CoolProp/IF97