Should feature macro be added in kernel language extensions

In OpenCL 3.0 feature macros were added but however, the extension spec has remained with the following statement:

> A unique name string of the form "cl_khr_" is associated with each extension. If the extension is supported by an implementation, this string will be present in the implementation’s CL_PLATFORM_EXTENSIONS string or CL_DEVICE_EXTENSIONS string.

As a matter of fact, that doesn't regulate EXT and vendor extensions...

Some extensions start to appear with feature macros such as `cl_ext_float_atomics` while others stay with `cl_ext_`.

Could we avoid different schemes for macros and just use one of the schemes?

The issue cites the OpenCL 3.0 feature-macro convention and the extension specification's extension-name statement; begin by comparing those rules with the existing EXT and vendor examples. Done means deciding whether a single macro naming scheme is required and documenting that decision in the relevant specification text.

Written by the indexing model from the issue text.