Fix __uuidof handling on non-type template parameter in C++17

Clang used to pass the base lvalue of a non-type template parameter
to the template instantiation phase when the base part is __uuidof
and it's running in C++17 mode.
However, that drops its LValuePath, and unintentionally transforms
&__uuidof(...) to __uuidof(...).

This CL fixes that by passing whole expr. Fixes PR24986.

https://reviews.llvm.org/D46820?id=146557
Patch from Taiju Tsuiki <tzik@chromium.org>!

llvm-svn: 332614
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index a5f6b3f..8f31602 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -6245,7 +6245,7 @@
       // -- a predefined __func__ variable
       if (auto *E = Value.getLValueBase().dyn_cast<const Expr*>()) {
         if (isa<CXXUuidofExpr>(E)) {
-          Converted = TemplateArgument(const_cast<Expr*>(E));
+          Converted = TemplateArgument(ArgResult.get());
           break;
         }
         Diag(Arg->getLocStart(), diag::err_template_arg_not_decl_ref)