clang-cl rejects dllimport on explicit member template specialization

[zmodem]

Bugzilla Link	21406
Version	unspecified
OS	Windows 2000
CC	@zahiraam

Extended Description

Consider:

struct S {
template void def() {}
};

struct T {};

template<> __declspec(dllimport) void S::def() {}

clang-cl rejects this, but MSVC accepts it. In test/SemaCXX/dllimport.cpp, there are comments suggesting we should only reject this for MinGW, but we end up rejecting it always.

(Issue 210136 may or may not be related)

[zmodem]

(Issue 210136 may or may not be related)

That should've been http://llvm.org/PR20136, a.k.a. #20510 after the github migration.