Add command-buffer context query

Introduce query `CL_COMMAND_BUFFER_CONTEXT_KHR` for the
`cl_context` associated with a command-buffer.

This PR uses enum value `0x1299` which is also attempting
be used by another command-buffer PR
KhronosGroup#850
However, that PR still needs review so would prefer
to use that enum here as `0x1299` is contiguous with
the other command-buffer query enums, and I can find a new
value for PR KhronosGroup#850

Closes KhronosGroup#898

ext/cl_khr_command_buffer.asciidoc

@@ -20,6 +20,7 @@ This extension adds the ability to record and replay buffers of OpenCL commands.
 | *Date*     | *Version* | *Description*
 | 2021-11-10 | 0.9.0     | First assigned version (provisional).
 | 2022-08-24 | 0.9.1     | Specify an error if a command-buffer is finalized multiple times (provisional).
+| 2023-03-31 | 0.9.2     | Introduce context query {CL_COMMAND_BUFFER_CONTEXT_KHR} (provisional).
 |====
 
 ==== Dependencies
@@ -422,6 +423,7 @@ CL_COMMAND_BUFFER_NUM_QUEUES_KHR                   0x1295
 CL_COMMAND_BUFFER_REFERENCE_COUNT_KHR              0x1296
 CL_COMMAND_BUFFER_STATE_KHR                        0x1297
 CL_COMMAND_BUFFER_PROPERTIES_ARRAY_KHR             0x1298
+CL_COMMAND_BUFFER_CONTEXT_KHR                      0x1299
 
 // cl_event command-buffer enqueue command type
 CL_COMMAND_COMMAND_BUFFER_KHR                      0x12A8
@@ -1590,6 +1592,10 @@ _param_value_ by {clGetCommandBufferInfoKHR} is described in the table below.
   or the implementation may return a property value of 0 (where 0 is used to
   terminate the properties list).
 
+| {CL_COMMAND_BUFFER_CONTEXT_KHR}
+| {cl_context_TYPE}
+| Return the context associated with _command_buffer_.
+
 |====
 
 {clGetCommandBufferInfoKHR} returns {CL_SUCCESS} if the function is executed

xml/cl.xml

@@ -1728,7 +1728,7 @@ server's OpenCL/api-docs repository.
         <enum value="0x1296"             name="CL_COMMAND_BUFFER_REFERENCE_COUNT_KHR"/>
         <enum value="0x1297"             name="CL_COMMAND_BUFFER_STATE_KHR"/>
         <enum value="0x1298"             name="CL_COMMAND_BUFFER_PROPERTIES_ARRAY_KHR"/>
-            <unused start="0x1299" comment="Reserved for MR199"/>
+        <enum value="0x1299"             name="CL_COMMAND_BUFFER_CONTEXT_KHR"/>
             <unused start="0x129A" end="0x129F" comment="Available to use"/>
         <enum value="0x12A0"             name="CL_MUTABLE_COMMAND_COMMAND_QUEUE_KHR"/>
         <enum value="0x12A1"             name="CL_MUTABLE_COMMAND_COMMAND_BUFFER_KHR"/>