true iff all types Ts are the same.
static assert(allSameType!()); static assert(allSameType!(int)); static assert(allSameType!(int, int)); static assert(allSameType!(int, int, int)); static assert(allSameType!(float, float, float)); static assert(!allSameType!(int, double)); static assert(!allSameType!(int, float, double)); static assert(!allSameType!(int, float, double, real)); static assert(!allSameType!(short, int, float, double, real));