Non-standard `RT` namespace is exposed in `sycl` namespace

[AlexeySachkov]

It looks like the following code:

llvm/sycl/include/sycl/detail/pi.hpp

Lines 259 to 260 in 321c733

	// For shortness of using PI from the top-level sycl files.
	namespace RT = sycl::detail::pi;

Brings RT namespace into sycl namespace - whilst that is not explicitly prohibited by the spec, it should be considered as a bad tone according to discussion in KhronosGroup/SYCL-Docs#137

[dm-vodopyanov]

Just a note: #9837 fixes only one usage of RT namespace. There are also

llvm/sycl/include/sycl/detail/pi.hpp

Line 244 in b3e0428

namespace RT = sycl::detail::pi;

and

llvm/sycl/unittests/helpers/PiMock.hpp

Line 52 in b3e0428

namespace RT = detail::pi;

[marcin-smuklerz-mobica]

Just a note: #9837 fixes only one usage of RT namespace. There are also

llvm/sycl/include/sycl/detail/pi.hpp

Line 244 in b3e0428

namespace RT = sycl::detail::pi;

and

llvm/sycl/unittests/helpers/PiMock.hpp

Line 52 in b3e0428

namespace RT = detail::pi;

I initially thought it is related to the exactly one mentioned in report. I will work on removal of others.

[dm-vodopyanov]

@marcin-smuklerz-mobica, thanks!