[llvm] [SYCL] Add libsycl, a SYCL RT library implementation project (PR #144372)

[Kseniya Tikhomirova via llvm-commits]

================
@@ -0,0 +1,64 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file contains the declaration of the macros defining attributes for
+/// exported methods and defining API namespaces.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef __LIBSYCL_DETAIL_CONFIG_HPP
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KseniyaTikhomirova wrote:

good catch, thanks. we have some macro like "__SYCL_DEVICE_ONLY" that have to have double underscore because it is defined by compiler. And it should be kept this way.
But the rest, the macro you are pointing too - don't need double underscores. I will update it, thank you!

https://github.com/llvm/llvm-project/pull/144372