Fix template instantiation of attributes. More specifically, fix the case

Fix template instantiation of attributes.  More specifically, fix the case
where an attribute is attached to a forward declaration of a template function,
and refers to parameters of that declaration, but is then inherited by the
definition of that function.  When the definition is instantiated, the
parameter references need to be remapped.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@164710 91177308-0d34-0410-b5e6-96231b3b80d8