It seems that the implicit instantiation is working well in vcl,
thanks to the changes fsm made a while ago. Given this, is there still
a need for the explicit instantiation in vcl?
Explicit instantiation in VXL itself is manageable, since "we" wrote
all the templates. The standard library implementations, on the other
hand, differs significantly from platform to platform. Normally,
reasonably standards conforming implementations will implicitly
instantiate everything correctly. However, trying to explicitly
instantiate can create problems with figuring out dependencies in the
headers. (The library implementors are allowed to have whatever
interdependencies they want, and we can't rely on them.)
I suggest we take out the explicit instatiation in *vcl*, but leave it
in for the rest of vxl.