PR20625: Instantiate static constexpr member function of a local struct in a...

PR20625: Instantiate static constexpr member function of a local struct in a function template earlier.

This is necessary in order to allow the use of a constexpr member function, or
a member function with deduced return type, of a local class within a
surrounding instantiated function template specialization.

Patch by Michael Park!


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@236063 91177308-0d34-0410-b5e6-96231b3b80d8