What is the meaning of VCL_CAN_DO_IMPLICIT_INSTANTIATION? From the
tests, it is actually checking if overloading of templated functions
works, not if the compiler will implicitly instantiate things. All the
compilers on the dashboard can implicitly instatiate
things. Otherwise, most of vil would not work.
So, shall we rename that test to VCL_CAN_OVERLOAD_TEMPLATE_FUNCTIONS
and always allow VCL_USE_IMPLICIT_TEMPLATES?