PR37680: fix faulty assertion condition.

When looking up a template name, we can find an overload set containing a
function template and an unresolved non-type using declaration.

llvm-svn: 334106
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index c759c96..64f45af 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -7292,6 +7292,7 @@
   for (UnresolvedSetIterator I = Begin; I != End; ++I) {
     NamedDecl *D = *I;
     assert(isa<FunctionTemplateDecl>(D) ||
+           isa<UnresolvedUsingValueDecl>(D) ||
            (isa<UsingShadowDecl>(D) &&
             isa<FunctionTemplateDecl>(D->getUnderlyingDecl())));
     *Storage++ = D;