CP023 Accessor aliases, revision 0.2

In order to reduce the verbosity of programming with SYCL accessors,
this proposal aims to reduce the number of template parameters
to just 2 from the current 5.
It achieves this by slightly revising
how to treat read-only data
and adding alias templates
based on the access target.

1. Main changes
    * Default accessor template parameters
    * Simplify access modes
    * Alias templates based on access target
    * Extend the handler class
2. Accessor alias templates
    * `constant_buffer_accessor
    * `host_accessor`
3. Treat `const T` the same as `access::mode::read`
    * Simplifies a lot of code
4. Define implicit conversions for equivalent types
5. Implicit conversions that add `const`
6. Overload for `handler::require` that also takes an access mode
  * To weaken the access mode
8. Default all accessor template parameters
  * Expect the data type
  * Default to an accessor to global buffer with read-write access
  * Assumes accessors can be a placeholder without template parameter
9. Discussed some considerations and alternatives
10. Examples of reduced verbosity

Author: ProGTX

README.md

@@ -63,4 +63,4 @@ from this registry in the future.
 | CP020 | [Interop Task](interop_task/interop_task.md) | SYCL 1.2.1 | 16 January 2019 | 16 January 2019 | _Available since CE 1.0.5_ |
 | CP021 | [Default-Constructed Buffers](default-constructed-buffers/default-constructed-buffers.md) | SYCL 1.2.1 | 27 August 2019 | 5 September 2019 | _Draft_ |
 | CP022 | [Host Task with Interop capabilities](host_task/host_task.md) | SYCL 1.2.1 | 16 January 2019 | 20 January 2020 | _Final Draft_ |
-| CP023 | [Accessor aliases](accessor-alias/index.md) | SYCL 1.2.1 vendor extension  | 22 September 2019 | 5 March 2020 | _Work in Progress_ |
+| CP023 | [Accessor aliases](accessor-alias/index.md) | SYCL Next (after 1.2.1) | 22 September 2019 | 9 March 2020 | _Work in Progress_ |

accessor-alias/index.md

@@ -4,7 +4,9 @@
 |-------------|--------|
 | Name | Accessor aliases |
 | Date of Creation | 22 September 2019 |
-| Target | SYCL 1.2.1 vendor extension |
+| Revision | 0.2 |
+| Latest Update | 9 March 2020 |
+| Target | SYCL Next (after 1.2.1) |
 | Current Status | _Work in Progress_ |
 | Reply-to | Peter Žužek <[email protected]> |
 | Original author | Peter Žužek <[email protected]> |
@@ -17,4 +19,4 @@ in order to reduce accessor verbosity.
 
 ## Versions
 
-[Version 1](sycl-2.2/index.md)
+[Revision 0.2](sycl-2.2/index.md)