Reviewing flexelint output for the recently added vmin/vmax macros
made apparent that vmin_t/vmax_t basically used typeof((cast)var),
which makes for an unnecessary de-tour via typeof.

We change the min/max macros to explicitly pass the type for the
temporary variables such that typeof() is only needed for vmin/vmax.

Being at it, we also reduce the min/max case to just one take macro
("take the min/max of ...") as they only differed in a single
character, the operator.