When determining template instantiation arguments within a function

When determining template instantiation arguments within a function
template (not a specialization!), use the "injected" function template
arguments, which correspond to the template parameters of the function
template. This is required when substituting into the default template
parameters of template template parameters within a function template.

Fixes PR9016.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@127092 91177308-0d34-0410-b5e6-96231b3b80d8