Modifies OpenCL 3.0 optional core feature macro definitions so that
they are set analogously in C++ for OpenCL 2021.
This change aims to achieve compatibility between C++ for OpenCL
2021 and OpenCL 3.0.
Differential Revision: https://reviews.llvm.org/D108704
This patch adds possibility to define OpenCL C 3.0 feature macros
via command line option or target setting.
Reviewed By: Anastasia
Differential Revision: https://reviews.llvm.org/D95776