Clang builtin utility `__remove_address_space` now works if generic
address space is not supported in C++ for OpenCL 2021.
Differential Revision: https://reviews.llvm.org/D110155
This change provides a way to conveniently declare types that have
address space qualifiers removed.
Since OpenCL adds address spaces implicitly even when they are not
specified in source, it is useful to allow deriving address space
unqualified types.
Fixes llvm.org/PR45326
Differential Revision: https://reviews.llvm.org/D106785